β-Galactosidase of Propionibacterium shermanii

摘要: Ten strains of Propionibacterium shermanii were tested for β-galactosidase (β-gal) activity. Of these ten strains, five yielded enhanced enzyme activity when cell suspensions treated with toluene-acetone; on solvent treatment, the remaining lost a considerable portion found in whole-cell suspensions. By using strain yielding decreased upon explanations loss sought through assays possible alternative β-galactoside utilization mechanisms. When this was assayed β-D-phosphogalactoside galactohydrolase by orthonitrophenyl-β-D-galactopyranoside-6-PO4 as substrate, either lower or indifferent compared β-gal determined simultaneously. Cell P. 7 and 22 (strains chosen further work) grown separately individual substrates (lactose, glucose, galactose, sodium lactate) did not show significant differences Optimal temperature untreated toluene-acetone-treated 52 C. With 22, temperatures tested, maximal noted at 58 C solvent-treated cells 32 In cell-free extract (CFE) system, both exhibited pH around 7.5. CFE occurred 7.0; had very little effect CFE. Sodium potassium phosphate buffers assay system best two Mn2+ definitely stimulatory, but systems presence absence variable effects Maximal harvested after 28 h growth lactate broth. Sulfhydryl-group blocking agents inhibited CFE; inhibition partly reversed dithiothreitol.