Abstract
Activities of 7, 8-diaminopelargonic acid (DAPA) aminotransferase, responsible for DAPA synthesis from 7-keto-8-aminopelargonic acid (KAPA) in biotin biosynthesis by microorganisms, were examined in crude cell-free extracts from about 100 strains of bacteria. Brevibacterium divaricatum NRRL 2311 in particular showed significantly high enzyme activity. The enzyme from Br. divaricatum was purified about 5, 000-fold to homogeneity. Characterization of the purified enzyme from Br. divaricatum was performed. The purified enzyme had absorption maxima at 320 nm and 410 nm, as well as at 280 nm. The molecular weight of the enzyme was determined to be 24, 000. Only S-adenosyl-L-methionine showed activity as an amino donor, while L-methionine, which was also active with the crude cell-free extract, showed no activity. 7-Amino-8-ketopelargonic acid was only one-hundredth as active as KAPA as an amino acceptor. Both pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate were effective as cofactors. The enzyme activity was strongly inhibited by typical inhibitors of PLP enzyme. An obvious repression of enzyme synthesis was observed on the addition of biotin to the culture medium.
