Betaine aldehyde dehydrogenase kinetics partially account for oyster population differences in glycine betaine synthesis

Betaine aldehyde dehydrogenase (BADH), the terminal enzyme of the glycine betaine synthetic pathway was purified 245-fold from the mitochondria of Atlantic and Chesapeake Bay oyster populations acclimated to 350 mosm, using ammonium sulfate precipitation, anion exchange, and affinity chromatography. BADH from both populations functions at; its maximum rate at 50-55 degrees C over a broad pH range (7.5-9). BADH activity is also modulated by increased [Na+] and [K+]. Although BADH from both populations has a similar V-max, BADH from Bay oysters has a substantially lower affinity for its substrate, betaine aldehyde, (K-m = 0.36 mM), than BADH from Atlantic oysters (K-m = 0.1 mM). Despite kinetic differences, BADH from both Atlantic and Chesapeake Bay oysters have the same molecular weight based on electrophoretic analysis. These differences in BADH enzyme kinetics between the two oyster populations probably partially explain the lower glycine betaine synthesis rates and concentrations in Chesapeake Bay oysters. (C) 2000 Wiley-Liss, Inc.