Lamprey fructose-1,6-bisphosphate aldolase: characterization of the muscle-type and non-muscle-type isozymes

To study evolutionary aspects of fructose-1,6-bisphosphate (Fru-1,6-P2) aldolase during deuterostomian evolution, we have purified and characterized aldolases from the muscle and liver of lamprey (Entosphenus japonicus). Aldolase from the skeletal muscle and liver was identified to be the muscle-type isozyme and the non-muscle-type isozyme that was encoded by cDNAs M8 and L3, respectively, as described previously (Zhang, R., Yatsuki, H., Kusakabe, T., Iwabe, Miyata, T., Imai, T., Yoshida, M., and Hori, K., J. Biochem. 117, 545-553, 1995). The muscle-type isozyme has properties similar to vertebrate aldolase A, while the non-muscle-type isozyme shows a similarity to bacterial class I aldolase and vertebrate aldolase C but not to aldolase B, the liver-type aldolase, in terms of kinetic parameters: the Kcat values toward Fru-1,6-P2 and Fru-1-P, the Fru-1,6-P2/Fru-1-P activity ratio, and the Km values toward these substrates. The two enzymes have tetrameric forms with a molecular mass of approximately 160,000 and have similar pH optimum. The muscle-type and non-muscle-type isozymes from the tissues show different electrophoretic mobility; the muscle-type isozyme moves much faster than the non-muscle-type isozyme toward anodic side. The recombinant muscle-type and non-muscle-type aldolases gave similar characteristics as those from the tissues. The results presented in this paper, together with the data presented in the previous paper, strongly suggest that in lamprey it is possible to have two types of aldolase isozymes rather than one or three isozymes.