Comparative analysis of malate dehydrogenases ofDrosophila melanogaster

✍ Scribed by Stephen J. O'Brien

• Publisher: Springer
• Year: 1973
• Tongue: English
• Weight: 765 KB
• Volume: 10
• Category: Article
• ISSN: 0006-2928
• DOI: 10.1007/bf00485765

✦ Synopsis

The malate dehydrogenases of D. melanogaster have been resolved into a cytoplasmic form (cMDH) and a mitochondrial matrix form (mMDH). Flies homozygous for allozyme variants exhibit isozymes of cMDH detected by starch gel electrophoresis and acrylamide gel isoelectric focusing. The basis of these isozymes was investigated, and the results suggest either conformational or epigenetic modification of isozymes. The probable structural gene for cMDH (Mdh-1) has been mapped genetically by allozyme variants to 11-35-t-3 and cytologically by monitoring gene dosage in segmental aneuploids to between 28D and 29F on II-L of the Drosophila salivary gland chromosome map. The structural gene for m M D H is neither identical to nor in the near chromosomal proximity of Mdh-1. Nevertheless, the two enzymes exhibit markedly similar properties with respect to (1) catalytic activity, (2) pH optima, (3) pH optimum shift in response to different ionic environments, and (4) molecular weight as determined by sucrose density gradient sedimentation.

The resolution of multiple forms of enzymes in a variety of systems and species has provided a particularly sensitive monitor of genetic and epigenetic differentiation in eukaryotes. Isoenzyme variation has been observed generally on two levels: (1) as tissue and/or developmental differences (e.g., Markert,