Multiple Forms of Glycosidases in the Normal and Pathological States

Abstract

Multiple forms of α- and β-galactosidase, α- and β-glucosidase, α- and β-hexosaminidases, α-mannosidase, α-fucosidase, and α-iduronidase of human tissues are surveyed. Their relationship to known storage disorders of glycolipid, glycoprotein, and mucopolysaccharide metabolism are discussed. A sub-unit hypothesis is presented to explain the interrelationships of multiple forms of β-N-acetylhexosaminidases that may be of wider application to include other glycosidases.

Neuronal N-acetyl-β-D-glucosaminidase. Evidence for its biosynthesis in vitro

“…5b), the proportions represented by a given glucosaminidase component in each of them differed considerably (Table 4). Thus at 1 min, glucosaminidase B represented more than twice the amount of glucosaminidase A in fraction Mic FT-S, whereas the reverse was true in fraction S. At 5min, the glucosaminidase B/A ratio in fraction Mic FT-S reached a value close to unity, while remaining unchanged in fraction S. Webelieve that thesefindings are consistent with the notion expressed above in the Results section, namely that at any one time, the different intracellular compartments contain different glucosaminidase components (Goldstone & Koenig, 1973, 1974. Thus our evidence suggests that glucosaminidase A, the preponderant component synthesized on the neuronal polyribosomes, resides preferentially in fraction S, whereas the less acidic component, glucosaminidase B, predominates in fraction Mic FT-S, where presumably it is en route to the lysosome.…”

Glycosidases from the culture medium of Physarum polycephalum

“…fi-N-Acetyl-i>hexosaminidases X and Y bear a striking resemblance to the A and B forms of the same enzyme from human tissues. The latter enzymes can also be separated by electrophoresis or ion-exchange chromatography and have similar molecular weight, pH optimum and Km values (Robinson, 1974). In contrast the more acidic form (Y) from P. polycephalum is the more stable of the two, whereas the more acidic human hexosaminidase (A) is less stable than form B.…”

The multiple forms and kinetic properties of the N-acetyl-β-d-hexosaminidases from colonic tumours and mucosa of rats treated with 1,2-dimethylhydrazine

“…The N-acetyl-fi-D-hexosaminidases (2-acetamido-2-deoxy-fi-D-glucoside acetamidodeoxyglucohydrolase, EC 3.2.1.30, and 2-acetamido-2-deoxy-fl-Dgalactoside acetamidodeoxygalactohydrolase, EC 3.2.1.53) from a variety of sources exist in two major forms designated A and B. These forms have been reported to be similar with respect to molecular weight, pH optima, Km values and behaviour towards inhibitors, but to differ in thermostability properties and electrophoretic mobility (Robinson, 1974). Various hypotheses have been put forward for a relationship between the two forms (e.g.…”