The allelic isozymes of hexose-6-phosphate dehydrogenase isolated from Fundulus heteroclitus: physical characteristics and kinetic properties.

Ira Ropson, D. A. Powers

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Hexose-6-phosphate dehydrogenase (H6PDH-A2; beta-D-glucose:NAD(P)+ oxido-reductase; E.C. 1.1.1.47) of the teleost Fundulus heteroclitus (L.) shows clinal allelic variation along the east coast of North America. Three of the major allelic isozymes have been purified and compared for native molecular weight, subunit molecular weight, isoelectric point, thermal stability, and steady-state kinetic properties (pH 8.0 and 25 degrees C). Significant differences were found among the allelic isozymes for isoelectric point, thermal stability, and some kinetic parameters. The predominant allelic isozyme in northern populations (H6PDH-AcAc) was found to be more sensitive to heat denaturation than were the predominant homozygous allelic isozymes isolated from southern populations (H6PDH-AaAa and H6PDH-AbAb). The H6PDH-AcAc allelic isozyme had both a significantly greater Km for glucose-6-phosphate than did either of the southern phenotypes and a significantly greater Km for NADP+ and Ki of NAD+ than did one of the southern phenotypes (H6PDH-AaAa). While the allelic isozymes are functionally nonequivalent, it is not yet known whether these differences are reflected at higher levels of biological organization.

Original languageEnglish (US)
Pages (from-to)171-185
Number of pages15
JournalMolecular Biology and Evolution
Volume6
Issue number2
StatePublished - Jan 1 1989

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Genetics

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