NADP+-dependent acetaldehyde dehydrogenase fromZymomonas mobilis

摘要

An NADP+-linked acetaldehyde dehydrogenase (EC 1.2.1.4) from the ethanol producing bacteriumZymomonas mobiliswas purified 180-fold to homogeneity. The enzyme is a cytosolic protein with an isoelectric point of 8.0 and has an apparent molecular weight of 210000. It showed a single band in sodium dodecylsulfate gel electrophoresis with a molecular weight of 55000, which indicates that it consists of four probably identical subunits. The apparentKmvalues for the substrate acetaldehyde were 57 μM and for the cosubstrate NADP+579 μM. The enzyme was almost inactive with NAD+as cofactor. Several other aldehydes besides acetaldehyde were accepted as a substrate but not formaldehyde or trichloroacetaldehyde. In anaerobically grown cells ofZymomonas mobilisthe enzyme showed a specific activity of 0.035 U/mg protein but its specific activity could be increased up to 0.132 U/mg protein by adding acetaldehyde to the medium during the exponential growth phase or up to 0.284 U/mg protein when cells were grown under aeration. The physiological role of the enzyme is discusse