Class III alcohol dehydrogenase from Saccharomyces cerevisiae: Structural and enzymatic features differ toward the human/mammalian forms in a manner consistent with functional needs in formaldehyde detoxication

Abstract

Alcohol dehydrogenase class III (glutathione-dependent formaldehyde dehydrogenase) from Saccharomyces cerevisiae was purified and analyzed structurally and enzymatically. The corresponding gene was also analyzed after cloning from a yeast genome library by screening with a probe prepared through PCR amplification. As with class III alcohol dehydrogenase from other sources, the yeast protein was obtained in two active forms, deduced to reflect different adducts/modifications. Protein analysis established N-terminal and C-terminal positions, showing different and specific patterns in protein start positions between the human/mammalian, yeast, and prokaryotic forms. K _m values with formaldehyde differ consistently, being about 10-fold higher in the yeast than the human/mammalian enzymes, but compensated for by similar changes in κ _cat values. This is compatible with the different functional needs, emphasizing low formaldehyde concentration in the animal cells but efficient formaldehyde elimination in the microorganisms. This supports a general role of the enzyme in formaldehyde detoxication rather than in long-chain alcohol turnover.