Abstract

Choline dehydrogenase (CD), the first enzyme of the glycine betaine synthetic pathway, was measured in a mitochondrial lysate from gill tissue from Atlantic and Chesapeake Bay oysters acclimated to both 350 and 750 mosm. CD from both populations functions at its maximum rate at 30 degrees C and pH 8.75. Although CD from both populations has a similar affinity for its substrate, choline (K(m) = 15.7 mM), CD V(max) from Atlantic oysters is twice that from Bay oysters. In addition, the CD K(m )doubles and the V(max) increases four-fold in both oyster populations acclimated to 750 mosm. CD activity is competitively inhibited by both betaine aldehyde and glycine betaine. The differences in CD kinetics between the two oyster populations help to account for the lower glycine betaine synthesis rates and concentrations in Chesapeake Bay oysters. CD cannot function rapidly enough to saturate the enzyme, betaine aldehyde dehydrogenase (BADH), immediately downstream, and, therefore, CD kinetics limit the rate of glycine betaine synthesis in oysters. J. Exp. Zool. 286:250-261, 2000.

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call