Coexistence of two kinds of 6-phospho-beta-galactosidase in the cytosol of Lactobacillus gasseri JCM1031--purification and characterization of 6-phospho-beta-galactosidase II.

Lactobacillus (L.) gasseri JCM1031 has 2 kinds of 6-phospho-beta-galactosidase (P-beta-gal) in the cytosol. P-beta-gal I was already isolated and characterized for our previous paper [Biosci. Biotech. Biochem., 60, 139-141 (1996)]. Another, P-beta-gal II, was purified to homogeneity through several liquid chromatographic steps for this paper. The molecular mass of the purified enzyme was estimated to be 58 kDa by SDS-PAGE. The Km and V(max) for ONPGal-6P were 0.76 mM and 86.0 mumol/min/mg, respectively. Reducing reagents and Fe2+ ion activated the enzyme, but PCMB, Zn2+, and Hg2+ ions, and alkylation reagents strongly inhibited it. Twenty-five residues of the N-terminal amino acid sequence of the enzyme were identified. P-beta-gal II was different from P-beta-gal I in several characteristics.