Francis M. Dickinson

THE ALD6 GENE OF SACCHAROMYCES CEREVISIAE ENCODES A CYTOSOLIC, MG2+-ACTIVATED ACETALDEHYDE DEHYDROGENASE

The deduced translation product of an open reading frame on the left arm of chromosome XVI of Saccharomyces cerevisiae, with the systematic name of YPL061w, is 500 amino acids in length and shares significant homology with aldehyde dehydrogenases. Amino acids 2 to 16 of the protein encoded by YPL061w were found to be identical to the N‐terminal 15 amino acids of the purified cytosolic, Mg2+‐activated acetaldehyde dehydrogenase (ACDH) of S. cerevisiae. This enzyme is thought to be involved in the production of acetate from which cytosolic acetyl‐CoA is then synthesized. Deletion of YPL061w was detrimental to the growth of haploid strains of yeast; an analysis of one deletion mutant revealed a maximum specific growth rate (in complex medium containing glucose) of one‐third of that displayed by the wild‐type strain. Mutants deleted in YPL061w were also unable to use ethanol as a carbon source. As expected, the cytosolic, Mg2+‐activated ACDH activity had been lost from the mutants, although the mitochondrial, K+‐activated ACDH was readily detected. YPL061w has been registered with the name of ALD6 in the Saccharomyces Genome Database and the nucleotide sequence submitted to GenBank as part of accession number U39205.

Some comparisons of pig and sheep liver cytosolic aldehyde dehydrogenases

1. The pig enzyme was purified to homogeneity and was found to be a tetramer of apparently identical subunits. 2. The pig enzyme was found to contain 1 mol NADH/mol enzyme which is tightly bound, which is not directly involved in catalysis and which so far has not been removed from the enzyme so as to produce an active apoenzyme. 3. The pig enzyme seems to contain only one functioning active site/tetramer. 4. The pig and sheep enzymes are compared in respect of NADH binding, substrate specificity, immunological response and surface charge.

On the photoinactivation of alcohol oxidase from alkane-grown Candida tropicalis

Abstract The process of photoinactivation of alcohol oxidase is insensitive to oxygen and to temperature in the range 0–25°C. The process is, however, wavelength dependent. Irradiation and inactivation do not cause any significant change to the visible absorption spectrum. Reaction of the enzyme with sodium sulfite or photoreduction in the presence of EDTA and either 5′-deazaflavin or lumiflavin 3-acetate under anaerobic conditions causes extensive bleaching of the visible spectrum of the enzyme and also protects it from photoinactivation. The presence of substrate under anaerobic conditions also provides very effective protection, but in this case there is no detectable change in the visible spectrum of the enzyme associated with the increase in stability to light.