Subunit interaction: a molecular basis of heterosis.
Acid phosphatase, a dimeric enzyme, in Drosophila malerkotliana was studied in isogenic flies to explore the molecular basis of heterosis. As the enzyme activity in heterozygotes is 34% more than that in the better parent (S/S), heterosis is indicated. Vmax, Km, and Ki values are 14.60, 3.6 X 10(-4) M, and 0.45 X 10(-4) M, respectively, for the enzyme from F/S flies and 11.80, 4.0 X 10(-4) M, and 0.37 X 10(-4) M, respectively, for the enzyme from S/S flies. Thus heterosis for enzyme activity results from a better enzyme in F/S flies. The higher efficiency and better quality of the enzyme in F/S flies were traced to the heterodimeric allozyme, present only in heterozygotes. Enzyme activity, Vmax, Km, and Ki values are 0.739, 42.1; 3.6 X 10(-4) M, and 0.50 X 10(-4) M, respectively, for the heterodimeric and 0.513, 36.8; 4.1 X 10(-4) M, and 0.37 X 10(-4) M, respectively, for the better parental homodimeric allozyme. On an equimolar basis the enzyme activity of the heterodimer is 44% higher than that of the better homodimer. The better performance of the heterodimer is probably a reflection of superior conformation resulting from interaction between component subunits (F and S polypeptides).
Trehan
K S
KS
Department of Genetics, Punjab Agricultural University, Ludhiana, India.
Gill
K S
KS
D000135:Acid Phosphatase / Q000235:genetics* / Q000378:metabolism; D000483:Alleles; D000818:Animals; D004330:Drosophila / Q000201:enzymology / Q000235:genetics*; D005260:Female; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D006823:Hybrid Vigor; D006824:Hybridization, Genetic; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male
D046911:Macromolecular Substances; D000135:Acid Phosphatase