Rates of spontaneous cleavage of glucose, fructose, sucrose, and trehalose in water, and the catalytic proficiencies of invertase and trehalas.

ABSTRACT: Most of the early experimental work on enzyme kinetics was based on the properties of yeast invertase (beta-fructo-furanosidase, EC 3.2.1.26), whose robust activity(1) (together with the availability of a continuous polarimetric assay) enabled Michaelis and Menten to establish the existence of a quantitative relationship between the rate of an enzyme reaction and the concentration of its substrate.(2) To appreciate the proficiency of an enzyme as a catalyst, it is also desirable to have information about the relative rates of the catalyzed and uncatalyzed reactions.(3) Surprisingly, the literature discloses no report of the rate of spontaneous hydrolysis of sucrose (although there have been many studies of the acid-catalyzed reaction).(4) That information would be of special interest in view of the remarkable resistance to hydrolysis (t1/2 approximately 10(7) y),(5) of the 1-4 "head-to-tail" glycosidic linkages that join the common glucose polymers cellulose, chitin, amylose, and glycogen. Thus, polysaccharide hydrolases (e.g., beta-amylase) generate the largest rate enhancements that are known to be produced by hydrolytic enzymes that operate without the assistance of metals or other cofactors.(6) Here, we describe the uncatalyzed hydrolysis of sucrose and trehalose, in which the constituent monosaccharides are symmetrically joined, by a "head-to-head" glycosidic linkage between their carbonyl groups (Chart ).

SUBMITTER: Wolfenden R 

PROVIDER: S-EPMC2664835 | biostudies-other | 2008 Jun

REPOSITORIES: biostudies-other