The influence of structure on the hydrolysis of substituted phenyl α-d-glucosides by α-glucosidase

Abstract

Nath & Rydon (1954) investigated the influence of structure on the hydrolysis of some substituted phenyl P-D-glucosides by ,B-glucosidase, correlating measured values of the kinetic constants for the enzymic hydrolysis, based on the classical theory of Michaelis & Menten (1913), with the substituent constants (Hammett, 1940), a, for the substituents in the phenyl group. The present paper describes a similar study of the hydrolysis of some substituted phenyl OC-D-glucosides by the a-glucosidase of brewer's yeast. A kinetic investigation of ac-glucosidase was carried out by Jsaiev (1926), who studied the hydrolysis of maltose by this enzyme and concluded that Michaelis-Menten kinetics were not strictly obeyed. However, Halvorson & Elias (1958) found that such kinetics were followed in the hydrolysis of p-nitrophenyl Oc-D-glucoside by the oc-glucosidase of Saccharomyces italicus (K, = 0-28 mM). The justification for our use of the Michaelis-Menten theory in interpreting our experimental results is discussed below. Substituted phenyl OC-D-glucosides are much more difficult to prepare in a state of purity than their fanomers, and for this reason the present work has involved only 10 substrates, as compared with the 21 studied by Nath & Rydon (1954); the preparation of the substrates is described by Hall, Hollingshead & Rydon (1961). EXPERIMENTAL Preparation of Oc-glucosidase a-Glucosidase was extracted from brewer's yeast by a modification of the method of Willstatter & Bamann (1926). After autolysis of the yeast with ethyl acetate, oc-glucosidase and fl-fructofuranosidase were absorbed on alumina

Effects of deuterium substitution α and β to the reaction centre, 18O substitution in the leaving group, and aglycone acidity on hydrolyses of aryl glucosides and glucosyl pyridinium ions by yeast α-glucosidase. A probable failure of the antiperiplanar-lone-pair hypothesis in glycosidase catalysis

“…The results with aryl glucosides show no systematic dependence of either logkca1. or log (kcat./Km) on the pKa of the departing phenol, correlation coefficients of 0.62 and 0.19 respectively being obtained; the five data points are adequate to confirm that the random variation of kinetic parameters with substrate structure observed with ten substrates by Hall et al (1962) was not a consequence of catalysis by several isoenzymes not separable by the techniques of the time.…”

The β-galactosidase-catalysed hydrolyses of β-d-galactopyranosyl pyridinium salts. Rate-limiting generation of an enzyme-bound galactopyranosyl cation in a process dependent only on aglycone acidity

“…with aglycone acidity, and Dahlquist et al (1969) have found an a-deuterium kinetic isotope effect (kHIkD) of 1.01±0.01 for the hydrolysis of phenyl ,B-D-glucopyranoside by this enzyme. Poor Hammett correlations have, however, also been found for brewer's yeast a-glucosidase (Hall et al, 1962), a-maltosidase (Suetsugu et al, 1971), mammalian ,B-glucuronidase (Watanabe & Suzuki, 1970;Wang & Touster, 1972), and fungal ,B-xylosidase (van Wijnendaele & De Bruyne, 1970).…”

Inhibitory properties of polyphenols in Malus “Winter Red” crabapple fruit on α‐glucosidase and α‐amylase using improved methods

“…The use of pNPG as a substrate for α-glucosidase activity assays began in the 1950s and mainly focused on yeast glycosidases (Hall et al, 1962;Robertson & Halvorson, 1957). Later, this method was adapted to measure the inhibitory properties of polyphenols on αglucosidase in vitro because the method is convenient and the pNG that is a product of enzymatic decomposition of pNPG has a large range of linear relationship between the concentration and absorbances (Ambreen et al, 2020).…”