Purification and partial characterization of 7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase and 7,8-dihydropteroate synthase from Escherichia coli MC4100

The enzymes 7,8-dihydroxymethylpterin-pyrophosphokinase (HPPK) and 7,8-dihydropteroate synthase (DHPS), which act sequentially in the folate pathway, were purified to homogeneity from crude extracts of Escherichia coli MC4100. The enzymes represent less than 0.01% of the total soluble protein. HPPK was purified greater than 10,000-fold; the native enzyme appears to be a monomer with a molecular mass of 25 kDa and a pI of 5.2. DHPS was purified greater than 7,000-fold; the native enzyme has an apparent molecular mass of 52 to 54 kDa and is composed of two identical 30-kDa subunits. The amino-terminal sequences for both enzymes have been determined.