Biochemical and genetic characterization of kynurenine formamidase fromDrosophila melanogaster

✍ Scribed by Gordon Paul Moore; David T. Sullivan

• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 763 KB
• Volume: 16
• Category: Article
• ISSN: 0006-2928
• DOI: 10.1007/bf00484718

✦ Synopsis

The molecular weight forms of kynuren&e formamidase were studied both genetically and biochemically. Formamidase I (native molecular weight 60,000) was purified using ( NH4 ) 2 S04 and p H fractionation, D EAE-cellulose chromatography at two different pH's, hydroxylapatite chromatography, and Sephadex G-IO0 gel filtration. Its subunit molecular weight, as determined by SDS gel electrophoresis, is 34,000, indicating that formamidase I is a dimer. Its Km is 1.87 × 10 -3 M. Its isoelectric point is pH 5.3. Its amino acid composition is reported. Formamidase H (native molecular weight 31,000) was partially purified using techniques similar to those above. Its Km is 2.31 × lO-3M. The response of formamidase activity to change in gene dosage was measured in segmental aneuploids generated in the second, third, and X chromosomes. Two separate chromosomal regions were identified which when present in extra dosage result in an elevation of the level of formamidase activity close to that predicted for the addition of a structural gene in a two-gene system. These tentative map positions were substantiated by demonstration that addition of one of the regions, 25A-27E, causes a 50% elevation in the relative amount of formamidase II. Addition of the other region, 91B-93F, causes a similar elevation in the relative amount of formamidase L A model of the evolutionary origin of the two forms is presented, and the significance of these results to this model is discussed.