[Isolation and properties of maltase from Saccharomyces cerevisiae-II]

Maltase from Saccharomyces cerevisiae-II was purified by ion-exchange chromatography on DEAE-Sephadex A-50 and isoelectric focusing. The purification procedure resulted in two enzyme isoforms with pI of 5.35 and 5.3 and identical specific activities. The molecular weights of the isoforms as determined by SDS polyacrylamide gel electrophoresis and gel filtration through Sephadex G-100 are 60 000 and 55 000, respectively. Both isoforms were electrophoretically polydisperse. The maltase isoforms are glycoproteins containing 1.5-2% of glucosamine and 5-8% (isoform A) and 2-3% (isoform B) of neutral sugars. Using paper chromatography and glucose oxidase, it was shown that glucose is an indispensable constituent of neutral sugars in both isoforms.