Purification and properties of an inducible beta-galactosidase isolated from the yeast Kluyveromyces lactis

Abstract

was purified 80-fold from the yeast Kluyveromyces lactis induced for this enzyme by growth on lactose. When the purified enzyme was subjected to electrophoresis on an acrylamide gel in the presence of sodium dodecyl sulfate, one protein with an apparent molecular weight of 135,000 was observed. The enzyme has a sediimentation coefficient of 9.68. This I)galactosidase and the one from Escherichia coli are not antigenically related. Maximal enzyme activity requires Na+ and Mn2' and a reducing agent. ft-Galactosidase has Km values of 12 to 17 and 1.6 mM for lactose and o-nitrophenyl-fB-D-galactoside, respectively. The hydrolase and transgalactosylase activities of the enzyme are similar to those of E. coli ,B-galactosidase.

Assay Conditions Effect on β‐Galactosidase Activity from Kluyveromyces lactis

“…This was not the case when reconstituted NFDM was used as the assay medium, probably due to the stabilizing effects of the milk proteins (Dahlqvist et al, 1977;Mahoney and Adamchuk, 1980). Also, certain milk proteins have a high affinity for copper (Aulakh and Stine, 1966), a strong inhibitor of yeast lactase (Wiseman, 1975;Dickson et al, 1979). Added potassium ions affected the hydrolytic action of pgalactosidase using the milk and buffered assays (Fig.…”

“…0 Formulated in pti 6.5 potassium phosphate buffer made in tap water. proteins -were shown to have activating and/or stabilizing effects on yeast lactases (Dahlqvist et al, 1977;Dickson et al, 1979, Mahoney andAdamchuck, 1980;Jacober-Pivarnik and Rand, 1984), other milk components, such as calcium and zinc, have shown inhibitory effects (Wiseman, 1975;Dickson et al, 1979;Mozaffar et al, 1985). Increased enzyme activity (151%) was observed when assay preparation was in 0.08M phosphate buffer prior to assay in skim milk.…”

Stability of β‐Galactosidase from Aspergillus oryzae and Khyveromyces lactis in Dry Milk Powders

“…ACTIVITY OF P-GALACTOSIDASES has been measured spectrophotometrically using o-nitrophenyl-P-D-galactopyranoside (ONPG) as substrate (Dickson et al, 1979). Also, using lactose as substrate one could measure glucose or galactose produced (Richmond et al, 1981;Kleyn and Trout, 1984).…”

Development and Evaluation of Whole‐Cell Yeast Lactase for Use in Dairy Processing

“…1). Based on the specific activity of pure lactase (139 Ulmg protein; Dickson et al, 1979), the enzyme content of the cells would be 4.3%. Yeast biomass levels ranged from 17-19 g/L, representing an average specific yield of 0.45 glg of carbohydrate substrate.…”