Porphyrins and Bile Pigments: Metabolism and Disorders Dr
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Evidence for the Role of Endogenous Carbon Monoxide in Memory Processing
Evidence for the Role of Endogenous Carbon Monoxide in Memory Processing M. C. Cutajar and T. M. Edwards Downloaded from http://mitprc.silverchair.com/jocn/article-pdf/19/4/557/1816404/jocn.2007.19.4.557.pdf by guest on 18 May 2021 Abstract & For a decade and a half, nitric oxide (NO) has been impli- number of electrophysiological investigations have concluded cated in memory processing across a wide variety of tasks and that endogenous CO is involved in long-term potentiation. species. Comparatively, endogenously produced carbon mon- Although not evidence for a role in memory per se, these oxide (CO) has lagged behind as a target for research into the studies did point to the possible importance of CO in mem- pharmacological processes underlying memory formation. This ory processing. In addition, there is now evidence to suggest is surprising given that CO is formed in memory-associated that endogenous CO is important in avoidance learning and brain regions, is structurally similar to NO, and along with possible for other tasks. This review therefore seeks to pro- NO can activate guanylate cyclase, which is an enzyme well mote endogenous CO as a potentially important target for characterized in memory processing. Nevertheless, a limited memory research. & INTRODUCTION important in memory processing (Kemenes, Kemenes, Carbon monoxide (CO) is traditionally thought of as Andrew, Benjamin, & O’Shea, 2002; Izquierdo et al., an air pollutant. Indeed, inhalation of environmental 2000; Bernabeu et al., 1997; Kendrick et al., 1997). By CO in sufficient quantities may lead to intoxication detailing the evidence for CO production in the hippo- through the production of carbonmonoxyhemoglobin, campus, its role in synaptic plasticity and those few which results in decreased oxygen storage and trans- behavioral studies implicating CO in memory consoli- port in the bloodstream. -
Chapter 5 High-Pressure Stopped-Flow Kinetic Studies of Nnos
Probing the dynamics and conformational landscape of neuronal nitric oxide synthase A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy in the Faculty of Life Sciences 2013 Anna Sobolewska-Stawiarz Contents Contents ...................................................................................................................... 2 List of Figures ............................................................................................................. 6 List of Tables ............................................................................................................ 10 Abstract ..................................................................................................................... 12 Declaration ................................................................................................................ 13 Copyright Statement ................................................................................................ 13 Acknowledgements ................................................................................................... 14 List of Abbreviations ............................................................................................... 15 List of Amino Acids Abbreviations ........................................................................ 17 CHAPTER 1. INTRODUCTION ........................................................................... 18 1.1 Nitric oxide synthase ......................................................................................... -
Hyperbilirubinemia
Porphyrins Porphyrins (Porphins) are cyclic tetrapyrol compounds formed by the linkage )). of four pyrrole rings through methenyl bridges (( HC In the reduced porphyrins (Porphyrinogens) the linkage of four pyrrole rings (tetrapyrol) through methylene bridges (( CH2 )) The characteristic property of porphyrins is the formation of complexes with the metal ion bound to nitrogen atoms of the pyrrole rings. e.g. Heme (iron porphyrin). Proteins which contain heme ((hemoproteins)) are widely distributed e.g. Hemoglobin, Myoglobin, Cytochromes, Catalase & Tryptophan pyrrolase. Natural porphyrins have substituent side chains on the eight hydrogen atoms numbered on the pyrrole rings. These side chains are: CH 1-Methyl-group (M)… (( 3 )) 2-Acetate-group (A)… (( CH2COOH )) 3-Propionate-group (P)… (( CH2CH2COOH )) 4-Vinyl-group (V)… (( CH CH2 )) Porphyrins with asymmetric arrangement of the side chains are classified as type III porphyrins while those with symmetric arrangement of the side chains are classified as type I porphyrins. Only types I & III are present in nature & type III series is more important because it includes heme. 1 Heme Biosynthesis Heme biosynthesis occurs through the following steps: 1-The starting reaction is the condensation between succinyl-CoA ((derived from citric acid cycle in the mitochondria)) & glycine, this reaction is a rate limiting reaction in the hepatic heme synthesis, it occurs in the mitochondria & is catalyzed by ALA synthase (Aminolevulinate synthase) enzyme in the presence of pyridoxal phosphate as a cofactor. The product of this reaction is α-amino-β-ketoadipate which is rapidly decarboxylated to form δ-aminolevulinate (ALA). 2-In the cytoplasm condensation reaction between two molecules of ALA is catalyzed by ALA dehydratase enzyme to form two molecules of water & one 2 molecule of porphobilinogen (PBG) which is a precursor of pyrrole. -
Characterisation of Bilirubin Metabolic Pathway in Hepatic Mitochondria Siti Nur Fadzilah Muhsain M.Sc
Characterisation of Bilirubin Metabolic Pathway in Hepatic Mitochondria Siti Nur Fadzilah Muhsain M.Sc. (Medical Research) 2005 Universiti Sains Malaysia Postgrad. Dip. (Toxicology) 2003 University of Surrey B.Sc.(Biomed. Sc.) 2000 Universiti Putra Malaysia A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2014 School of Medicine ABSTRACT Bilirubin (BR), a toxic waste product of degraded haem, is a potent antioxidant at physiological concentrations. To achieve the maximum benefit of BR, its intracellular level needs to be carefully regulated. A system comprising of two enzymes, haem oxygenase-1 (HMOX1) and cytochrome P450 2A5 (CYP2A5) exists in the endoplasmic reticulum (ER), responsible for regulating BR homeostasis. This system is induced in response to oxidative stress. In this thesis, oxidative stress caused accumulation of these enzymes in mitochondria — major producers and targets of reactive oxygen species (ROS) — is demonstrated. To understand the significance of this intracellular targeting, properties of microsomal and mitochondrial BR metabolising enzymes were compared and the capacity of mitochondrial CYP2A5 to oxidise BR in response to oxidative stress is reported. Microsomes and mitochondrial fractions were isolated from liver homogenates of DBA/2J mice, administered with sub-toxic dose of pyrazole, an oxidant stressor. The purity of extracted organelles was determined by analysing the expressions and activities of their respective marker enzymes. HMOX1 and CYP2A5 were significantly increased in microsomes and even more so in mitochondria in response to pyrazole-induced oxidative stress. By contrast, the treatment did not increase either microsomes or mitochondrial Uridine-diphosphate-glucuronosyltransferase 1A1 (UGT1A1), the sole enzyme that catalyses BR elimination through glucuronidation. -
Porphyrins & Bile Pigments
Bio. 2. ASPU. Lectu.6. Prof. Dr. F. ALQuobaili Porphyrins & Bile Pigments • Biomedical Importance These topics are closely related, because heme is synthesized from porphyrins and iron, and the products of degradation of heme are the bile pigments and iron. Knowledge of the biochemistry of the porphyrins and of heme is basic to understanding the varied functions of hemoproteins in the body. The porphyrias are a group of diseases caused by abnormalities in the pathway of biosynthesis of the various porphyrins. A much more prevalent clinical condition is jaundice, due to elevation of bilirubin in the plasma, due to overproduction of bilirubin or to failure of its excretion and is seen in numerous diseases ranging from hemolytic anemias to viral hepatitis and to cancer of the pancreas. • Metalloporphyrins & Hemoproteins Are Important in Nature Porphyrins are cyclic compounds formed by the linkage of four pyrrole rings through methyne (==HC—) bridges. A characteristic property of the porphyrins is the formation of complexes with metal ions bound to the nitrogen atom of the pyrrole rings. Examples are the iron porphyrins such as heme of hemoglobin and the magnesium‐containing porphyrin chlorophyll, the photosynthetic pigment of plants. • Natural Porphyrins Have Substituent Side Chains on the Porphin Nucleus The porphyrins found in nature are compounds in which various side chains are substituted for the eight hydrogen atoms numbered in the porphyrin nucleus. As a simple means of showing these substitutions, Fischer proposed a shorthand formula in which the methyne bridges are omitted and a porphyrin with this type of asymmetric substitution is classified as a type III porphyrin. -
Bilirubin Metabolism (Lecture 8)
Bilirubin Metabolism (Lecture 8) Excretory function of bile Bile is a medium for excretion of many substances as bile pigments, cholesterol, many drugs, toxins and various organic substances as copper and zinc. These substances are then eliminated in the feces. One of these substances excreted in bile is the greenish yellow pigment bilirubin. This is a major end product of hemoglobin degradation. It’s highly soluble in all cell membranes & is also very toxic. Therefore, its excretion in the bile is one of the very important functions of the liver. FATE OF RED BLOOD CELLS Life span of RBCs in blood stream is 60-120 days. Senescent RBCs become too fragile to exist longer in the circulatory system, their cell membranes rupture and they are phagocytosed and/or lysed. Normally, lysis occurs extravascularly in the reticuloendothelial system subsequent to RBC phagocytosis. Lysis can also occur intravascularly (in blood stream). The hemoglobin is first split into globin & heme. The AA formed from breakdown of globin are stored in the body. Metabolism of bilirubin The heme ring is opened to give: 1. Free iron that is transported in the blood by transferrin and stored in the body as a reservoir for erythropoiesis. 2. Bile pigments: The 1st pigment is biliverdin but it is rapidly reduced by biliverdin reductase to free bilirubin which is gradually released into the plasma. The free bilirubin is hydrophobic, immediately combines with plasma proteins (mainly albumin and globulin) forming a water soluble compound called hemobilirubin (unconjugated bilirubin) which is rapidly transported to hepatocytes for further metabolism. Even when bound to albumin it’s called free bilirubin. -
Magnesium-Protoporphyrin Chelatase of Rhodobacter
Proc. Natl. Acad. Sci. USA Vol. 92, pp. 1941-1944, March 1995 Biochemistry Magnesium-protoporphyrin chelatase of Rhodobacter sphaeroides: Reconstitution of activity by combining the products of the bchH, -I, and -D genes expressed in Escherichia coli (protoporphyrin IX/tetrapyrrole/chlorophyll/bacteriochlorophyll/photosynthesis) LUCIEN C. D. GIBSON*, ROBERT D. WILLOWSt, C. GAMINI KANNANGARAt, DITER VON WETTSTEINt, AND C. NEIL HUNTER* *Krebs Institute for Biomolecular Research and Robert Hill Institute for Photosynthesis, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, United Kingdom; and tCarlsberg Laboratory, Department of Physiology, Gamle Carlsberg Vej 10, DK-2500 Copenhagen Valby, Denmark Contributed by Diter von Wettstein, November 14, 1994 ABSTRACT Magnesium-protoporphyrin chelatase lies at Escherichia coli and demonstrate that the extracts of the E. coli the branch point of the heme and (bacterio)chlorophyll bio- transformants can convert Mg-protoporphyrin IX to Mg- synthetic pathways. In this work, the photosynthetic bacte- protoporphyrin monomethyl ester (20, 21). Apart from posi- rium Rhodobacter sphaeroides has been used as a model system tively identifying bchM as the gene encoding the Mg- for the study of this reaction. The bchH and the bchI and -D protoporphyrin methyltransferase, this work opens up the genes from R. sphaeroides were expressed in Escherichia coli. possibility of extending this approach to other parts of the When cell-free extracts from strains expressing BchH, BchI, pathway. In this paper, we report the expression of the genes and BchD were combined, the mixture was able to catalyze the bchH, -I, and -D from R. sphaeroides in E. coli: extracts from insertion of Mg into protoporphyrin IX in an ATP-dependent these transformants, when combined in vitro, are highly active manner. -
Biochemistry I Enzymes
BIOCHEMISTRY I 3rd. Stage Lec. ENZYMES Biomedical Importance: Enzymes, which catalyze the biochemical reactions, are essential for life. They participate in the breakdown of nutrients to supply energy and chemical building blocks; the assembly of those building blocks into proteins, DNA, membranes, cells, and tissues; and the harnessing of energy to power cell motility, neural function, and muscle contraction. The vast majority of enzymes are proteins. Notable exceptions include ribosomal RNAs and a handful of RNA molecules imbued with endonuclease or nucleotide ligase activity known collectively as ribozymes. The ability to detect and to quantify the activity of specific enzymes in blood, other tissue fluids, or cell extracts provides information that complements the physician’s ability to diagnose and predict the prognosis of many diseases. Further medical applications include changes in the quantity or in the catalytic activity of key enzymes that can result from genetic defects, nutritional deficits, tissue damage, toxins, or infection by viral or bacterial pathogens (eg, Vibrio cholerae). Medical scientists address imbalances in enzyme activity by using pharmacologic agents to inhibit specific enzymes and are investigating gene therapy as a means to remedy deficits in enzyme level or function. In addition to serving as the catalysts for all metabolic processes, their impressive catalytic activity, substrate specificity, and stereospecificity enable enzymes to fulfill key roles in additional processes related to human health and well-being. Proteases and amylases augment the capacity of detergents to remove dirt and stains, and enzymes play important roles in producing or enhancing the nutrient value of food products for both humans and animals. -
Determination of Urinary Porphyrin by DEAE-Cellulose Chromatography and Visual Spectrophotometry
A n n a l s o f C l i n i c a l a n d L a b o r a t o r y S c i e n c e , Vol. 4, No. 1 Copyright © 1974, Institute for Clinical Science Determination of Urinary Porphyrin by DEAE-Cellulose Chromatography and Visual Spectrophotometry MARTHA I. WALTERS, P h .D.* Ohio Valley Hospital, Steubenville, OH 43952 ABSTRACT A simple, reliable and rapid method for the isolation and determination of urinary porphyrins is described. Both uroporphyrin and coproporphyrin are quantitatively adsorbed by DEAE cellulose. Urobilinogen, urobilin, and bili rubin are removed with sodium acetate. The isolated porphyrins, eluted with 1 N HC1, are measured spectrophotometrically, and the excretion is related to that of creatinine. Porphyrin excretion was studied in normal adults and children, and in patients with disorders of porphyrin metabolism ( e.g., in lead poisoning, hemolytic anemia, hepatic disease and porphyria) in order to eval uate the method. The coefficient of variation of replicate analyses of a sample containing 200 ¡xg porphyrin per gm creatinine was 3.5 percent. The correlation coefficient between 83 duplicate analyses was 0.993. Introduction or adsorption onto an adsorbant followed Patients with porphyria show great in by elution. Methods combining extraction creases in the excretion of uroporphyrin, and adsorption have been the most com coproporphyrin and their precursors indi monly used,3’12 but procedures employing cating a primary abnormality of porphyrin ion-exchange chromatography,11’13 electro synthesis (figure 1). In addition to these phoresis,4’10 and thin-layer chromatogra disorders, there are a number of diseases phy15’16 also have been described. -
UTMB Testing Packet/Order Form
Galveston Porphyria Laboratory The University of Texas Medical Branch Galveston, Texas Instructions for Collecting, Processing and Shipping Samples for Porphyria Testing This packet contains the following: • Instructions for collecting, processing and shipping samples • Order form for testing • A primer on laboratory testing for porphyrias Updated 9 June 2021 Page 1 Instructions for Collecting, Processing and Shipping Samples I. Sample Collection and Processing GENERAL INSTRUCTIONS 1. Types of samples used for porphyria testing (For choice of tests, see the attached Primer): a. Urine – spot (random or single void) urine sample is recommended with no preservative. A first-void sample on arising in the morning is preferred. i. Creatinine is measured on all urine samples for “normalization” of the results. The amount of creatinine excreted every day is quite constant because it reflects muscle mass. Most adults excrete 1-2 grams of creatinine daily in urine. Expressing results per gram of creatinine corrects for variation in the hydration state of the patient over time. The sample should be light protected (e.g. by wrapping the container in aluminum foil) and immediately refrigerated or frozen. ii. A 24-hour collection is also suitable, but 5 gm of sodium carbonate (not sodium bicarbonate) should be added to the container before starting the collection, the container should be refrigerated and protected from light during the collection (e.g. by using a dark-colored plastic collection bottle). The total volume must be measured in a single container and only a portion (an “aliquot”) sent to the laboratory for testing. Detailed instructions on how to properly collect a 24-hour urine must be given verbally to the patient along with the container containing the preservative. -
Bilirubin Metabolism
Bilirubin Metabolism By Aseel .j.abdullah Introduction • Bilirubin is the orange-yellow pigment derived from senescent red blood cells. • It is a toxic waste product in the body. • It is extracted and biotransformed mainly in the liver, and excreted in bile and urine. • It is a bile pigment • Elevations in serum and urine bilirubin levels are normally associated with Jaundice. Erythrocytes become “old” as they lose their flexibility and increasingly rigid and fragile,they easily destruct during passage through tight circulation spots, especially in spleen, where the intra-capillary space is about 3 micron as compared to 8 micron of cell size RBCs useful life span is 100 to 120 days,After which they become trapped and fragment in smaller circulatory channels, particularly in those of the spleen. For this reason, the spleen is sometimes called the “red blood cell graveyard.” Dying erythrocytes are engulfed and destroyed by macrophages. Formation of Bilirubin • Primary site of synthesis:- SPLEEN : The Graveyard of Red Blood Cells • Secondary site of synthesis:- LIVER & BONE MARROW Pathophysiology RBCs Breakdown Hemoglobin Produces & Breakdown Heme Heme Oxygenase Biliverdin Biliverdin Reductase Bilirubin In Blood Unconjugated bilirubin • The bilirubin synthesized in – Lipid soluble spleen, liver & bone marrow – : limits excretion is unconjugated bilirubin. – 1 gm albumin binds 8.5 mg bilirubin • It is hydrophobic in nature so – Fatty acids & drugs can it is transported to the liver displace bilirubin as a complex with the – Indirect positive reaction plasma protein, albumin. in van den Bergh test • Most of the reabsorbed urobilinogen is taken up by the liver & is re-excreted in the bile. -
Design and Fine-Tuning Redox Potentials of Metalloproteins Involved in Electron Transfer in Bioenergetics
1 Design and Fine-tuning Redox Potentials of Metalloproteins Involved in Electron Transfer in Bioenergetics Parisa Hosseinzadeh and Yi Lu Abstract: 1. Introduction A significant portion of biological processes are involved with providing vital energy sources such as ATP, and controlling the flow of energy through living systems. These bioenergetics processes, the most important of which are photosynthesis and respiration, require electron transfer (ET) between different redox partners. Metalloproteins are one of the most widely used ET centers in biology. They can be classified into three major classes: cupredoxins, which include type 1 copper (T1Cu) proteins and CuA centers [1- 10], cytochromes [10-17], and iron-sulfur (FeS) proteins [10,18-24]. Each class of ET proteins transfer electrons between different redox partners which possess different reduction potentials (E°) (Figure 1). Therefore, the ET centers need to adjust their E° in a way that matches those of their redox partners. No single class of protein can cover the entire range of physiological E°, which is between ~ -1V, at which protons are reduced to H2, and 1V, at which water is oxidized to O2. Cupredoxins usually function at the high end of the E°, while FeS proteins are mostly involved in ET reactions possessing relatively low E° [10]. The E°’s of FeS proteins overlap significantly with those of cytochromes that often have intermediate E° among the three classes of ET proteins. Figure 1. Reduction potential range of metal centers in electron transfer metalloprotein. Adapted from ref. [10] 2 In this review, we first describe the importance of tuning E° of ET centers, including the metalloproteins described above.