ISSN:
1573-4927
Keywords:
human red-cell carbonic anhydrase I
;
widespread polymorphic frequency
;
Australian Aborigines
;
amino acid substitution
;
selective advantage
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Carbonic anhydrase I (EC 4.2.1.1) purified from the pooled packed red blood cells of 100 individuals typed as heterozygous for the common Australian Aboriginal carbonic anhydrase I variant CAI Australia-9 had a slightly higher specific CO2 hydratase or esterase (toward p-nitrophenyl acetate) activity than the normal component and a higher K m and V max using the esteratic substrate. The variant enzyme was slightly more resistant to heat inactivation. The extent of inhibition of both enzymes by the specific inhibitor acetazolamide was identical, as was their immunological behavior and the lability of the active-site zinc ion. The variant enzyme was more resistant to chloride inhibition. The physiological importance of this observation is discussed in the context of a proposed adaptive advantage of the variant gene in the arid western and central regions of Australia. The amino acid substitution in the Aboriginal variant of a glycine for an aspartic acid residue has been located at residue 8 from the N terminus (i.e., 8 Asp → Gly), by proteolytic and partial acid hydrolyses. The possible effects of this substitution on the structure and function of the molecule are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00484071
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