Purification and characterization of variant alcohol dehydrogenase isozymes from durum wheat

Three alcohol dehydrogenase (ADH) isozymes from embryos of the durum wheat cultivar Bijaga Yellow having the variant Adh-Alb allele were purified using (NH4)2SO4 precipitation, gel filtration, and ion-exchange chromatography. ADH is a dimeric enzyme. The variant isozyme ADH-1-1, which is a homodimer composed of alpha b monomers, was compared with ADH-1-5 (homodimer composed of beta a monomers), the product of Adh-B1, and the ADH-1-3 isozyme (alpha b beta a heterodimer) on a number of parameters including Km, substrate specificities, and molecular weights. No appreciable differences among the three isozymes were found, except for the faster electrophoretic mobility of alpha b alpha b dimers (ADH-1-1). The results indicate that the variant isozyme is the result of a mutation altering only the charge of the isozyme.