Comparative Study of Isoenzyme Formation of Bacterial β-Galactosidase

Abstract

The enzyme β-galactosidase was studied in crude extracts of Escherichia coli 3300, E. coli grown on a selenium and sulfur medium, Salmonella typhimurium F-lac, Serratia marcescens F-lac, S. marcescens P-lac, Proteus mirabilis F-lac, P. mirabilis P-lac, Aeromonas formicans , and Streptococcus lactis . The isoenzymes could be demonstrated by an alternative histochemical technique. Different isoenzyme patterns were found to be determined by the β-galactosidase structural gene and not by the cytoplasm within which the β-galactosidase was formed. In addition, the β-galactosidases from strains which form isoenzymes were more stable to heat and urea treatments than the enzyme formed by those organisms which produce reduced amounts of, or no, isoenzyme.