LINKING OF ISOZYME AND CLASS VARIABILITY PATTERNS IN THE EMERGENCE OFNOVEL ALCOHOL-DEHYDROGENASE FUNCTIONS - CHARACTERIZATION OF ISOZYMES IN UROMASTIX HARDWICKII
L. Hjelmqvist et al., LINKING OF ISOZYME AND CLASS VARIABILITY PATTERNS IN THE EMERGENCE OFNOVEL ALCOHOL-DEHYDROGENASE FUNCTIONS - CHARACTERIZATION OF ISOZYMES IN UROMASTIX HARDWICKII, European journal of biochemistry, 236(2), 1996, pp. 563-570
The nature of the isozyme differences in the class-I alcohol dehydroge
nase structure from the lizard, Uromastix hardwickii, was determined a
nd related to those in the human and horse enzymes, for which isozyme
structures have also been established. The Uromastix isozymes differ m
uch (at a total of 72 positions, 19%) but, in spite of this, have simi
lar properties and were not obtained resolved. Their structures were a
nalyzed in mixture, and the two sub-sets of peptides obtained could be
distinguished by evaluation of the recovery ratios within the peptide
pairs. The isozymes have class-I activities, with an ethanol dehydrog
enase activity of 0.6 U/mg and no formaldehyde dehydrogenase activity,
have typical class-I structures, and are composed of N-terminally ace
tylated 375-residue subunits (a and b). Importantly, variability patte
rns between the isozymes are reminiscent of those both in the other tw
o lines with isozymes (primates and horse) and in the class distinctio
ns of the enzyme. Hence, the variability pattern since the distant sta
ge of class-I emergence is also visible within the more recent isozyme
divergence, illustrating a continuity in the evolution of isozymes to
classes (and then to enzymes). The pattern also links the different l
evels of multiplicity and may suggest an acceptability in common to du
plications and mutations, compatible with the emergence of novel funct
ions.