Alcohol dehydrogenases and aldehyde dehydrogenases.

T h e structure, function and evolution of alcohol dehydrogenases and aldehyde dehydrogenases have been studied for several years. Recent progress o n these aspects has been considerable and allows extensive conclusions to be drawn about the relationships and properties of these enzymes. Further aspects have also become available for study, such as the regulation of enzyme expression and the analysis of additional forms at the crystallographic level. T h e major results are summarized in Table 1 and are discussed further below. Alcohol dehydrogetiase relatioriships Alcohol dehydrogenases constitute a complex set of enzymes related at different levels. The enzymes have been analysed in this department in collaboration with several groups. Structurally, initial discoveries (together with Jeffery) revealed that alcohol and polyol dehydrogenases are distantly related in two different families, one of ‘long-chain’ zinc-containing enzymes, and one of ‘short-chain’ non-zinccontaining enzymes (Jiirnvall et ul., 198 1 ). T h e latter family also includes at least one sugar dehydrogenase (Jiirnvall et al., 1984h). T h e zinc-containing family reveals three levels of gene duplication (Jiirnvall et ul., 1 9 8 7 ~ ) as schematically summarized in Fig. 1. These levels are as follows: an early level giving rise to the now distantly related alcohol/polyol dehydrogenases with about 25%) residue identity (Jeffery ef al., 1984); an inter-