Isophosphorylase and the Formation of Branched Polysaccharides

Bernfeld, P.; Meutémédian, A.

doi:10.1038/162618b0

Cited by 13 publications

(8 citation statements)

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“…Thus, considerably more than 50 per cent of the glucose units must be situated in end chains. This is thought to support the views of Bernfeld & Meutemedian (190,191) on the synthesis of branched molecules by joint action of phos phorylase and isophosphorylase. The present writer is not con vinced, however, that amylopectin can result from an equilibrium between the reversible actions of the two enzymes.…”

Section: Experiments By Flock and Bollmansupporting

confidence: 69%

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Nonoxidative Nonproteolytic Enzymes

Myrbäck¹

1949

Annu. Rev. Biochem.

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It has been, more or less, a tacit assumption that enzymes constitute only a small part of the protein of the living cell.Virtanen has pointed out that from our present knowledge of the quantities of enzymes it seems justifiable to conclude that in microorganisms practically all protein is enzyme protein. There fore, the formation of an adaptive enzyme should correspond to a decrease in some other enzyme or enzymes, presumably of a related type. Lowering of the protein content of the cell by starvation should decrease primarily the amounts of adaptable (dispensable) enzymes, whereas the indispensable (constitutive) enzymes should maintain their activity. Virtanen & De Ley (1) have determined saccharase in E. coli which is, in this case, an adaptive enzyme, and catalase, a typically constitutive enzyme. By nitrogen starvation the protein content of the cells could be materially decreased. The saccharase content fell rapidly but catalase activity was only slightly affected. Investigations by Bucher & Kaspers (2) on the photochemical splitting of carbon monoxide hemoglobin may throw light on the action of the protein carrier on the prosthetic groups of enzymes. Not only radiation absorbed by the hemin splits off carbon monoxide, but also radiation absorbed by the protein. In the photo inactivation of urease the effect is the same, if the quanta are absorbed by a few tyrosine or tryptophane residues or by all amino acids. It is suggested that transmission of absorbed activation energy may be one of the causes of the chemical activation of prosthetic groups by the carriers. Attention is called to a paper by Veldstra (3) on the interaction of "ergones" and substrates. Rothen's experiments on "enzyme action at a distance" were mentioned in Vol. XVII of this Review. New experiments (4) have been published which are thought to exclude the possibility of diffusion of the enzyme through the protecting layers. Mettler, however, points out (5) that the antigen films are not of constant 1 This review covers approximately the period from December, 1947 to De cember, 1948. 59 Annu. Rev. Biochem. 1949.18:59-86. Downloaded from www.annualreviews.org Access provided by Technische Universiteit Eindhoven on 02/02/15. For personal use only. Quick links to online content Further ANNUAL REVIEWS

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Section: Experiments By Flock and Bollmansupporting

confidence: 69%

“…Bernfeld & Me}ltemedian (190,191) have studied an enzyme "isophosphorylase," previously called "branching factor" (Cori) or "Q-enzyme" (Haworth et at. ), which synthesizes 1,6-a-glucosidic linkages from glucose-1-phosphate in presence of a suitable "germ."…”

Section: Experiments By Flock and Bollmanmentioning

confidence: 98%

Nonoxidative Nonproteolytic Enzymes

Myrbäck¹

1949

Annu. Rev. Biochem.

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“…The degree of branching of the polysaccharide obtained depends on the ratio of the concentrations of the two enzymes. The larger the relative amount of isophosphorylase, the more the polysaccharide formed is branched (16,18). Bailey and Whelan could not obtain an active preparation of isophosphorylase from potato (la).…”

Section: Isophosphorylasementioning

confidence: 99%

Enzymes of Starch Degradation and Synthesis

Bernfeld¹

1951

Advances in Enzymology - And Related Areas of Molecular Biology

326

172

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“…However, a fundamental difference is that while phosphorylase is able to cause chain growth or breakdown, no such action can be attributed to isophosphorylase. Bernfeld and Meutdmddian (18,20) suggest that by varying the ratio of phosphorylase t o isophosphorylase a series of amylopolysaccharides with different degrees of branching may be formed; others (146-148) argue that whether amylopectin or glycogen is formed by the simultaneous action of phosphorylase and isophosphorylase depends on whether conditions favor an irreversible or a reversible process. Bernfeld and Meutdmddian (18,20) suggest that by varying the ratio of phosphorylase t o isophosphorylase a series of amylopolysaccharides with different degrees of branching may be formed; others (146-148) argue that whether amylopectin or glycogen is formed by the simultaneous action of phosphorylase and isophosphorylase depends on whether conditions favor an irreversible or a reversible process.…”

Section: B Phosphorylase Plus Branching Factormentioning

confidence: 99%

“…Because of reports (17)(18)(19)(20) of the occurrence in potatoes of an enzyme (isophosphorylase) with similar cross-linking function, Barker, Bourne, Wilkinson, and Peat (7,8,162) recently have reinvestigated the action of the &-enzyme. They reported that neither the presence of inorganic phosphate, or phosphorylase, or glucose 1-phosphate influences the conversion of amylose to amylopectin by their purest preparations, that, therefore, &-enzyme does not synthesize cross linkages by a mwhanism of phosphate transfer, and that two distinct amylopectin-synthesizing systems may exist together in potatoes.…”

Section: Formation Of Branched Amylopolysaccharides and Dextrans Fmentioning

confidence: 99%