Comparative estimation of activity of two marker enzymes for determining the quality of brush border membrane fractions for in vitro binding assays in Culex quinquefasciatus (Say) mosquito larvae

Bacillus sphaericus (Bs) is a potential biolarvicide against several species of mosquito vectors as it synthesizes binary toxin (51 and 42 kDa proteins) during sporulation. Two marker enzymes (leucine aminopeptidase, LAP and alkaline phosphatue, ALKP) were evaluated for determining the quality of brush border membrane fractions (BBMF) for in vitro binding assays in Culex quinquefasciatus (Say) of Bs-susceptible, resistant and cross-hybrid larvae. The isolation of RBMF from these larval strains was good due to high protein concentration. Also, a high specific activity of LAP-enzyme was observed than the ALKP-enzyme and suggested that LAP is more reliable and appropriate marker enzyme for estimating quality of BBMF. The findings from in vitro binding experiments between the ¹²⁵I radioiabelled B. sphaericus binary toxin and BBMF from the Bs-susceptible, resistant and cross-hybrid also correlated the quality of BBMF.