Aspartate-β-Semialdehyde Dehydrogenase from Escherichia coli

Purification and General Properties

Authors


  • Definition. 1 enzyme unit, U, is defined as the quantity of enzyme able to reduce 1 μ;mol NADP+/min at 25°C in 0.02 M triethanolamine-HCl buffer, pH 8.

To whome correspondence should be addressed.

Abstract

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.

Abbreviations
NMR

nuclear magnetic resonance

dansyl

5-dimethylaminonaphthalene-1-sulfonyl

QAE

quaternary diethyl-(2-hydroxypropyl)aminoethyl

Enzymes
 

l-Aspartate-β-semialdehyde: NADP+ oxidoreductase (phosphorylating) (EC 1.2.1.11)

 

d-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating) (EC 1.2.1.12)

 

glucose-6-phosphate dehydrogenase (EC 1.1.1.49)

 

isocitrate dehydrogenase (NADP+) (EC 1.1.1.42)

 

aldehyde dehydrogenase (EC 1.2.1.3)

 

hydroxymethylglutaryl-CoA reductase (NADPH) (EC 1.1.1.34)

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