Studies on .BETA.-galactosidase. II. Purificaof .BETA.-of .BETA.-galactosidase from Macrophomina phaseoli and its enzymatic properties.

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Abstract
Acid .beta.-galactosidase (EC 3.2.1.23) was purified from the culture filtrate of M. phaseoli by column chromatography using DEAE-cellulose and Sephadex G-200, and isoelectric focusing. The purified enzyme was homogeneous on disc electrophoresis. The enzyme is considered to be a glycoprotein, because the mobility of the protein band coincided with that of sugar 1 in disc electrophoresis, and because sugar content was not varied before and after isoelectric focusing of the purified enzyme. The sugar content of the enzyme was estimated to be 12% with phenol-sulfuric acid method. The enzyme was most active at pH 5.0 and 60.degree. C, and stable over a pH range 4.0-8.0 and below 55.degree. C. The enzymatic activity was completely inactivated only by N-bromosuccinimide at 0.1 mM. Km value was determined to be 0.45 mM for o-nitrophenyl .beta.-D-galactopyranoside (ONPG) and 15 mM for lactose, and Vmax was calculated to be 93.6 .mu.mol .cntdot. min-1 .cntdot. mg-1 for ONPG and 54.5 .cntdot. mmol .cntdot. min-1 .cntdot. mg-1 for lactose.

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