Biochemical and Genetic Characterization of Betaine Aldehyde Dehydrogenase

Betaine aldehyde dehydrogenase (BADH) catalyzes the last step of betaine synthesis in chenopods: Betaine aldehyde + NAD(P) + H2O ⇄ Betaine + NAD(P)H + H+ BADH exists in spinach leaves as two isozymes: a major stromal form and a minor cytosolic form. A rare fast electrophoretic variant of the stromal enzyme was found by a germplasm survey; the variant enzyme differed from the common form in charge but not size. F1 hybrids between the variant and prevalent types showed a three-banded pattern. The F2 and BC1 ratios of parental to F1-hybrid phenotypes were 1:2:1 and 1:1, respectively, suggesting that 4: (a) stromal BADH is a dimer; (b) alleles of a single nuclear BADH gene encode subunits that associate randomly into homo- and heterodimers.