Purification of UDP-N-acetylenolpyruvoylglucosamine reductase from Escherichia coli by affinity chromatography, its subunit structure and the absence of flavin as the prosthetic group.

The enzyme UDP-N-acetylenolpyruvoylglucosamine reductase (EC 1.1.1.158) was purified to homogeneity from Escherichia coli by affinity chromatography on a NADP-agarose column. The evidence suggests that the enzyme (molecular weight 35,000) is composed of two nonidentical subunits of molecular weight 21,500 and 13,500, respectively. The absorption spectrum of the purified enzyme shows no absorption band around 450 nm and thus does not support the previous suggestions that the enzyme is a flavoprotein. However, the A280: A260 ratio gives a value of 0.86 which suggests the presence of tightly bound nucleotide. A quantitative transfer of tritium from 1,4-[4-3H]NADPH to UDP-N-acetylenolpyruvoylglucosamine to form UDP-N-E13H]acetylmuramic acid was also observed, which clearly shows that the enzyme is not a flavoprotein.