Induction of β-galactosidase in Streptomyces violaceus

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Abstract
Synthesis of β-galactosidase by Streptomyces violaceus was induced by D-galactose and L-arabinose, and to a lesser extent by lactose, D-arabinose, and methyl-β-D-galactopyranoside. The synthesis of the enzyme was linear and started to increase 2–3 h after induction by galactose, reaching a maximum after 5–7 h. The highest level of specific activity was observed in 2% galactose, with an increase of 45 times over the basal level in glycerol. Isopropyl-β-D-thiogalactopyranoside (IPTG) and methyl-β-D-thiogalactopyranoside (TMG) inhibited induction by D-galactose, but did not influence enzymatic activity. Cellular extracts hydrolyzed o-nitrophenyl-β-D-galactopyranoside, but did not significantly hydrolyze lactose, melibiose, p-nitrophenyl-α-D-galactopyranoside, p-nitrophenyl-β-D-fucoside, or p-nitrophenyl-β-D-glucopyranoside. Rifampicin and chloramphenicol inhibited β-galactosidase synthesis in non-preinduced and in pre-induced cells. The inhibition by chloramphenicol was reversible.

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