Polygalacturonase activity in must prepared from Muscat Bailey A (Bailey x
Muscat Hamburg) grapes increased markedly at one day after the addition of
yeast, whereas no enzyme activity was detected throughout fermentation in m
ust made from the juice alone. Polygalacturonase activity increased in must
s made using either fresh or heated skins. These results indicated that pol
ygalacturonase was produced by growing yeasts and that the skin fraction (s
kins and seeds) was necessary for production of the enzyme. Three polygalac
turonases (PG-I, II, and III) were separated from the skin fraction by DEAE
Sepharose Fast Flow column chromatography. PG-I released a monomer, dimer,
and trimer from the substrate polygalacturonic acid, whereas PG-II and III
released only the monomer. The optimal pH of both PG-I and II was 3.5, whe
reas that of PG-III was 4.5. The activities of PG-I, II, and III were parti
ally inhibited by SO2 and ethanol.