ENZYMIC DEGRADATION OF CEREAL HEMICELLULOSES. I. OBSERVATIONS ON THE Β-Glugosanase SYSTEM AND ITS DEVELOPMENT DURING MALTING

Abstract

An initial linear relationship between increases in reciprocal specific viscosity and in reducing group liberation has been confirmed for that aspect of /?-glucosanase activity which involves attack on /3-glucosan only at points remote from the ends of molecules, i.e., endo-/?-glucosanase activity; excess reducing groups over and above those calculated from this relation are ascribed to exo-/?-glucosanase and cellobiase, Prolonged endo-action gives progressive degradation of large molecules with ulti mate production of cellobiose and laminarlbiose; exo-action gives celloblose from the start. The presence of cellobiase makes glucose production inevitable. Different raw cereals show different proportions of endo-and exo-activity and of cellobiase, but barley is moderately rich in all three. During the malting of barley, endoactivity is enhanced 100-200 fold, and there is a measure of resistance to heat inactivation on the kiln. Available evidence suggests that the increase in exo-activity is only moderate, and this activity may be entirely suppressed by kilning. Cellobiase activity is variable, but has been found in all extracts and preparations examined.Methods for differential inactivation of endo-and exo-enzymes have been examined, but only the latter can be readily destroyed. Vol. 62, 1056] PREECE AND HOGGAN: /J-GLUCOSANASE SYSTEM OF CEREALS 487

Studies of viscosity as the probable factor involved in the improvement of certain barleys for chickens by enzyme supplementation

“…The enzyme causing cytoclastic attack on j8-glucan is called endo-/?-glucanase (Preece, Aitken and Dick, 1954) and, in addition to producing large fission products, it yields on prolonged action cellobiose, laminaribiose and a series of more complex saccharides (Preece and Hoggan, 1956;Preece and Garg, i960 and Preece, Garg and Hoggan, i960).…”

Development of Cytolytic Enzyme Activities During Germination of Different Barleys

“…Previously, Preece and Hoggan (1956), Bourne and Pierce (1970) and Bendelow (1971) have demonstrated the development of endo-B-glucanase (barley-B-glucan endohydrolase) activity in one or more barley cultivars during germination. Bass et al (1957) also reported large differences in this activity in barley and in green malt indicating that a large increase occurred during germination.…”

β-d-Glucan Hydrolase Activity in Zea Coleoptile Cell Walls

“…65, 1980 vironment. Mercury was without apparent effect on endoglucanolytic activity and a lack of sensitivity to sulfhydryl-specific reagents has been noted for other endoglucanases (19,20,28). We have examined endoglucanases from Bacillus, Rhizopus, and Phaseolus cell wall preparations and none display sensitivit7, in terms of altered activity or specificity, toward 100 uM Hg + (Huber, unpublished).…”

“…Concentrations exceeding 3 M, however, do not significantly increase activity yields nor further reduce cell wall protein levels (Huber, unpublished (14,28,34,36), and the lack of complete inhibition observed in some instances might be explained on the basis of the inhibitor employed (i.e. HgCl2 versus pCMB).…”