The specificity of barley limit dextrinase

Manners, D. J.; Rowe, Karen L.

doi:10.1042/bj1100035pa

Cited by 10 publications

(10 citation statements)

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“…These separated activities were given the respective names R-enzyme and limit dextrinase. Manners and coworkers [3,4] have subsequently confirmed the MacWilliam and Harris finding, with the same and with different plant extracts.…”

Section: Introductionsupporting

confidence: 61%

“…Our inability to correlate our own results with those of MacWilliam and Harris [2] and Manners and coworkers [3,4] has perhaps been overcome following a recent report by Manners, Marshall and Yellowlees [S] , where it is stated that amylopectin P-limit dextrin is a substrate for "limit dextrinase". This is contrary to the report by MacWilliam and Harris [2] but now permits an explanation of what limit dextrinase might be, since under its new definition, it has all the activities originally ascribed to Renzyme [ 11, save that of attacking amylopectin.…”

Section: Introductioncontrasting

confidence: 43%

“…We have no opinion on what is the activity in malted barley referred to by Manners and Sparra [4] as R-enzyme, and which is described as acting on amylopectin and its /I-dextrin, as judged by increases in intensity of iodine stain and degree of /3-amylolysis, but not acting on pullulan and o-limit dextrins. It is this activity that is in need of further investigation and renaming.…”

Section: Discussionmentioning

confidence: 96%

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On the specificity of starch debranching enzymes

1970

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Section: Introductionsupporting

confidence: 61%

Section: Introductioncontrasting

confidence: 43%

Section: Discussionmentioning

confidence: 96%

See 1 more Smart Citation

On the specificity of starch debranching enzymes

1970

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“…A branching enzyme extract from sweet corn (Zea mays) also acted on amylose and amylopectin but, because of the different pH and temperature optima of the reactions with amylose and amylopectin and the activation by citrate of only the amylose reaction, it was concluded that the extract contained a second branching activity [32]. This was further supported by differences in the heat stabilities and inhibitions by HgC1, of the activities with the two substrates and was subsequently confirmed by the separation of two activities by Manners et al [33]. The first activity branched amylose only and was designated as Q-enzyme, whilst the second activity was similar to the branching enzyme of yeast [34] in that it readily acted on amylose and amylopectin.…”

Section: Purification and Properties Of Potato And-enzymesupporting

confidence: 48%

Purification and Properties of Potato. alpha-1,4-Glucan 6-Glycosyltransferase (Q-Enzyme)

1972

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Potato Q-enzyme ( a-I ,4-glucan : a-1,4-glucan 6-glycosyltransferase) has been purified at least 430-fold. Its instability in the purified state was reversed by Cleland's reagent (dithiothreitol) and the preparation was essentially free of other starch-metabolising enzymes (a-amylase, a-glucosidase, D-enzyme and R-enzyme).Studies involving successive and simultaneous actions of &-enzyme and pullulanase on amylose showed that the final average unit-chain length and iodine stain of the products were almost identical, but gel filtration revealed that their chain-length distributions were Merent. Similarly, two amylopectin-like polysaccharides formed by the direct action of &-enzyme on amylose and by the combined action of &-enzyme and potato phosphorylase on glucose i -phosphate were debranched with pullulanase and their unit-chain length distributions compared by gel filtration with that of a debranched native amylopectin. I n neither case was the unit-chain profile of native amylopectin reproduced.The &-enzyme preparation has been shown to introduce additional branch points into amylopectin with the formation of a significant proportion of maltohexaosyl side chains. Evidence is presented that Q-enzyme and not a second branching enzyme is responsible for this action and a mechanism for the formation of the maltohexaosyl chains is proposed.Plant branching enzyme (&-enzyme, a-1,4-glucan : a-glucan 6-glycosyltransferase was first identified in potato [l], from which it was subsequently isolated in crystalline form [2,3]. Amorphous preparations have also been isolated from many higher plants [4-91. In vitro the branching enzyme converts amylose into an amylopectin-like polysaccharide which corresponds to native amylopectin in its average chain length, solubility, iodine staining ability and its extent of degradation by B-amylase [lo]. The enzyme splits an a-l,4-linkage in the amylose chain (donor molecule) and transfers the severed segment to a similar chain (acceptor molecule) with the formation of an a-1,B-branch point. It has not been determined whether the acceptor may be the remaining portion of the same amylose chain (intra-chain transfer) or another amylose molecule (inter-chain transfer). The transfer reaction appears to be irreversible ; the reconversion of 1,6-into 1,4-linkages has not been demonstrated 11-11.

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“…Denaturation of the polysaccharide may be the permissive cause of Q-enzyme action. Claims have been made of the conversion of amylopectin into glycogen by plant branching enzyme preparations [38,39]. Such conversion requires an approximate doubling of the content of branch linkage and halving of the average chain length.…”

Section: -Phosphate; ( -)mentioning

confidence: 99%

Purification and Properties of Potato 1,4‐α‐d‐Glucan: 1,4‐α‐d‐Glucan 6‐α‐(1,4‐α‐Glucano)‐Transferase

Borovsky

Smith

Whelan

1975

European Journal of Biochemistry

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Q‐Enzyme, the enzyme that synthesizes the 1,6‐α‐glucosidic branch linkages of amylopectin, has been purified from potato to near homogeneity. The molecular weight of the enzyme is 85000. The active enzyme is a monomer, with a molar activity at pH 7.0 and 24 °C of 15. The energy of activation is 25 kJ/mol below 15 °C, changing sharply to 63 kJ/mol above that temperature. Enzyme activity is not affected by Mg2+ or ATP. There are about 11 readily titratable sulfhydryl groups per molecule. The evidence that the enzyme is a single protein entity, without hydrolytic activity towards amylose, contrasts with an earlier report that Q‐enzyme consists of two components, a hydrolase with molecular weight 70000, and a transferase with molecular weight 20000. Q‐Enzyme acts on native and synthetic amyloses to give products resembling amylopectin in terms of average unit chain length, degree of β‐amylolysis and iodine stain. The profiles of the unit chains of these synthetic products are, however, different from that of native amylopectin. Additional branch linkages are introduced by Q‐enzyme into potato amylopectin, but the product bears no resemblance to phytoglycogen.

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The specificity of barley limit dextrinase

Abstract: 35P ofits conversion into fibrous hydroglucan (Houwink & Kreger, 1953). We thank Dr C. T. Bishop for a sample of glucan from Candida parap8ilo8i8 and Mrs E. F. Cruickshank for technical assistance.

Cited by 10 publications

References 0 publications

On the specificity of starch debranching enzymes

On the specificity of starch debranching enzymes

Purification and Properties of Potato. alpha-1,4-Glucan 6-Glycosyltransferase (Q-Enzyme)

Purification and Properties of Potato 1,4‐α‐d‐Glucan: 1,4‐α‐d‐Glucan 6‐α‐(1,4‐α‐Glucano)‐Transferase

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