Purification and characterization of two allozymic forms of octopine dehydrogenase from California populations ofMetridium senile

Summary In northern and southern California populations of the plumose sea anemone,Metridium senile, octopine dehydrogenase occurs in two allozymic forms and these forms are distributed in a highly population-specific manner; the frequency of the slow allele (ODH ¹⁰⁰) is 0.875 in the northern (Bodega Bay) population while the frequency of the fast allele (ODH ¹⁰³) in the southern population (Santa Barbara) is 0.125. Purification techniques resulted in an increase in purity of approximately 400 fold. The enzyme is a monomer ofM _r 35,000 to 40,000. Though there is some flexibility in the amino acid substrate which the enzyme uses (arginine and lysine react similarly), the specificity for the keto acid is limited to pyruvate.The kinetic characters of the two allozymes ofMetridium senile ODH are very different with respect to type of substrate saturation (Fig. 4 and 5) and apparent Michaelis constants (K _m) for pyruvate, lysine, arginine, and octopine (Table 5), product inhibition by octopine (Fig. 2), and optimal activity with respect to pH (Fig. 3). The properties of the slow and fast allozymes resemble the kinetic properties of cephalopod brain and muscle tissue-specific isozymes (Table 7). The kinetic data indicate that the slow allozyme would not allow a great deal of accumulation of octopine in vivo, while the fast allozyme is poised markedly towards octopine production.When the data presented in this study are compared to various physiological findings of other investigators, it becomes evident that the probable in vivo function of ODH in sea anemones is to act, in a manner analogous to vertebrate LDH, during the short-term anaerobiosis associated with muscle contraction and locomotion. The population-specific distribution and the different functional properties of the two ODH allozymes are most likely related to the different degree of tidal exposure which the two populations experience in nature. Only the slow allozyme possesses the regulatory properties which would allow a shift to the alternative anaerobic pathways utilized during these longer exposure periods.Abbreviations ODH octopine dehydrogenase - LDH lactate dehydrogenase - PHI phosphohexose isomerase