No. 3914, NOVEMBER 4, 1944 NATURE 581 Alleged Role of Fructofuranose in the ture of fructofuranoses and fructopyranoses. The recent demonstration that glucose-1-phosphate (Cori Synthesis of Levan ester) and fructose form a dynamic equilibrium with THE view was long widely entertained that cells sucrose and phosphoric acid in the presence of a. synthesize macromolecules of polysaccharides and specific enzyme8 corroborates this view. Addition of proteins by a reversion .of the process of hydrolysis. fructose to sucrose does not inhibit levan production It has been suggested accordingly that the synthesis from the latter, yet fructose itself, although it pre• of the polyfructoside levan specifically from aldo• sumably contains ready fructofuranose, is not con• side< >fructofuranosides (sucrose, raffinose) involves verted into levan by levansucrase7 • Similarly, levan• two distinct steps : first, hydrolysis of the substrate ; sucrase fails to form levan from reaction mixtures secondly, polymerization of fructofuranose b;r a con• in which fructofuranose is sustainedly liberated in densation involving removal of water1• Bacteria statu nascendi, for example, in reaction mixtures of which form levan from sucrose do so also from methyl gamma fructoside + yeast invertase, and of raffinose•. This polymerative type of sucrose de• inulin inulase. gradation is concurrent with an ordinary hydrolytic (c) Extracts of an Aerobacter, although they pro• inversions·'· The same banteria ferment !evans. duce levan from sucrose and hydro'yse the latter as Investigators might be tempted by these correlations well, do not hydrolyse levan. Thus they contain to consider the enzyme system, levansucrase, to be levansucrase and invertase but no polyfructosidase but a mixture of invertase and polyfructosidase. It (levanase) 7 • On the other hand, takadiastase and is shown below, however, that this view cannot be an extract of a Torula yeast have been found to valid. hydrolyse levan and inulin as well as sucrose, yet (a) Owen 5 added yeast invertase solution to cultures produced no levan from the latter. Thus they con• of bacteria growing in a sucrose medium. The tain invertase as well as polyfructosidase yet are addition did not augment but inhibited formation of without levansucrase. levan by the cells. The findings suggested that in• The conclusion is therefore indicated that fructo• vertase is not an essential component of the levan• furanose is not an intermediary of levan synthesis forming enzyme, but since it referred to living and from aldoside< :::- fructofuranosides. The view of proliferating cells a final conclusion in this respect macromolecular biosynthesis as a reversion of hydro• could not be drawn6 • The recent preparation of cell• lase action apparently fails to describe levan pro• free levansucrase from Aembacters has made it possible duction, even as it fails to depict the biological pro• to carry out Owen's experiment in conditions free duction of glycogen and starch. from the criticisms to which his earlier attempt is open. 8. HESTRIN. It has been found that addition to this levansucrase Chemistry Department, of yeast invertase in amount sufficient to double the Cancer Research Laboratories, rate of sucrose decomposition does not arfect levan Hebrew University, production in solutions containing a high initial con• Jerusalem. centration of sucrose (more than 5 per cent). In Aug. 28. solutions containing levan-formation-limiting con• 1 Smith, G., Proc. Linn. Soc.,.N.S. Wales, 26, 593 (1901). centrations of sucrose (less than 2 per cent), addition 'Hibbert, et al., Can. J. Res., 4, 221, 596 (1931). of yeast invertase to the levansucrase caused in• • Hestrin et al., Biochem. J., 37, 450 (1943); Nature, 149, 527 (1942). hibition, rather than augmentation, of levan pro• 'Hestrin and Avineri-Shapiro, Nature, 152, 49 (1943). duction. 'Owen, J. Bact., 8, 420 (1923). • Norman, "The Biochemistry of Cellulose, Lignin, Polyuronidf'll, etc.'' On the view that fructofuranose is the substrate (Oxford, 1937). actually polymerized by levansucrase, it is still 'Hestrin and Avineri-Shapiro, Biochem. J., 38, 2 (1944). possible to explain the failure of invertase to accel• • Isbell and Pigman, J. Res., U.S. Nat. Bur. Stand., 20, 773 (1938). erate levan production from a non-limiting concentra• ' Doudoroff, J. Biol. Chem., 151, 358 (1943). tion of sucrose by assuming that in this process hydrolysis, though essential, is not a rate-limiting step. This complicating possibility is eliminated A Blind Woodlouse where the rate of levan production is known to be dependent on the sucrose concentration. It is similarly WHEN examining some specimens of Armadillidium eliminated in reactions carried out on raftmose. vulgare (Latr.), kindly sent to me by Dr. H. W. Levan is produced much more slowly from rafLnose Howard of Cambridge from the University Farm, I noticed that a female specimen of the variety than from an equivalent concentration of sucrose7 • 1 If the reaction proceeds via fructofuranose, the rate• "Black type B" of Howard was entirely void of limiting step on raft"nose can only be hydrolysis, eyes or any trace of them. In this example there is subsequent steps by the terms of the theory being no trace of any visual elements or even pigment. identical for both sucrose and raffmose. Yet addition The chitin on the cephalon, where the eyes should be, to levansucrase of enough yeast invertase to render is very slightly convex, shelving down laterally and the rate of ratLnose hydrolysis by the enzyme mixture inwardly. equal to the rate of conversion of sucrose by levan• During the past thirty years, I have examined sucrase alone failed to augment, and in the long run many thousands of specimens referable to this species, inhibited, the rate of production of levan from but I have never met with one in which . the eyes raffinose. The conclusion is therefore confirmed that were absent, or in any other species of terrestrial invertase is irrelevant to levan production from isopod excepting in truly cavernicolous ones. sucrose and rarLnose by levansucrase. WALTER E. CoLLINGB. (b) There is further direct evidence that fructo• The Hollies, furanose is not a substrate which can be polymerized 141 Fulford Road, by levansucrase. Isbell and Pigman 8 have concluded York. on the basis of measurements of optical rotation that Oct. 2. fructose in aqueous solution is an equilibrium mix- 1 J. Genetics, 40, 83, pl. iv, fig. B (1940).

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