ISSN:
1573-4927
Keywords:
kynurenine
;
kynurenine formamidase
;
segmental aneuploidy
;
tryptophan catabolism
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract The molecular weight forms of kynurenine formamidase were studied both genetically and biochemically. Formamidase I (native molecular weight 60,000) was purified using (NH4)2SO4 and pH fractionation, DEAE-cellulose chromatography at two different pH's, hydroxylapatite chromatography, and Sephadex G-100 gel filtration. Its subunit molecular weight, as determined by SDS gel electrophoresis, is 34,000, indicating that formamidase I is a dimer. Its K m is 1.87×10−3 m. Its isoelectric point is pH 5.3. Its amino acid composition is reported. Formamidase II (native molecular weight 31,000) was partially purified using techniques similar to those above. Its K m is 2.31×10−3 m. 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 I. A model of the evolutionary origin of the two forms is presented, and the significance of these results to this model is discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00484718
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