Analysis of malate dehydrogenase isozymes from anuran amphibian ovary by isoelectric focusing.

The isozymes patterns of ovarian malate dehydrogenase (MDH) from various anuran amphibian series were analyzed by isoelectric focusing (IEF). Extensive variability was observed in both the soluble (sMDH) and mitochondrial (mMDH) patterns with as few as two and as many nine bands being visualized in different species. The mean pIs for sMDH ranged from 4.5 to 8.3 and those for mMDH fell between 5.1 and 8.2. The sMDHs are considerably more heat labile in Rana species living in northern latitudes compared to those from southern states. Inhibition with p-chlormercuribenzoate (PCMB) revealed the importance of sulfhydryl groups for the activity of sMDHs, while the functional requirement for these groups in mMDHs appears to be of lesser importance. Observations from these studies lend support to the accumulating evidence that Rana pipiens from such southern locations as New Mexico may have undergone speciation.