Proline Biosynthesis in Escherichia coli: Purification and Characterisation of Glutamate‐Semialdehyde Dehydrogenase

Abstract

Glutamate‐semialdehyde dehydrogenase, catalysing the reduction in vivo of γ‐glutamyl phosphate to glutamate 5‐semialdehyde in the pathway of proline biosynthesis in Escherichia coli, has been purified to homogeneity. High initial levels of the enzyme were achieved by using a multicopy ColEl‐proA,B hybrid plasmid. The protein has a molecular weight of 1.89 × l05 and consists of four identical subunits of molecular weight 4.7 × l04 each. The pH optimum is 7.0 and the protein is stable for at least 10 min between pH 6.0−9.0 and for long periods at pH 7.0. It is rapidly inactivated at temperatures greatcr than 50°C. The enzyme is very sensitive to inhibition by p‐chloromercuribenzoate, copper and nickel ions. Copyright © 1982, Wiley Blackwell. All rights reserved