Aspartate-β-semialdehyde dehydrogenase, from an Escherichia coli mutant derepressed for the biosynthesis of l-lysine, has been purified to homogeneity. Its isoelectric point is pH 4.3. This enzyme has a molecular weight of 77000 and is composed of two identical or highly similar subunits of molecular weight 38000 ± 2000.
Their N-terminal amino-acid sequence is Met-Lys-Asx-Val-Gly-. Three cysteine residues per subunit were detected: two are reactive in the native enzyme and one is partially protected by the substrate. Formation of an acyl-enzyme intermediate was also detected. Correlation of the 1H nuclear magnetic resonance spectrum of [4-2H]NADPH produced from [4-2H]NADP+ indicated that aspartate β-semialdehyde dehydrogenase transfers the pro-S hydrogen from NADPH (class B dehydrogenase). A short comparison with the corresponding yeast enzyme is given.
nuclear magnetic resonance
l-Aspartate-β-semialdehyde: NADP+ oxidoreductase (phosphorylating) (EC 188.8.131.52)
d-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating) (EC 184.108.40.206)
glucose-6-phosphate dehydrogenase (EC 220.127.116.11)
isocitrate dehydrogenase (NADP+) (EC 18.104.22.168)
aldehyde dehydrogenase (EC 22.214.171.124)
hydroxymethylglutaryl-CoA reductase (NADPH) (EC 126.96.36.199)