Purification and properties of pituitary gonadotropic hormone from Indian teleosts: Freshwater murrel ( Channa punctatus) and carp ( catla catla)

Abstract

Gonadotropic hormone (GtH) from the pituitaries of two widely different Indian teleosts, a freshwater murrel and a carp, was purified by solvent fractionation, Sephadex G-100 gel filtration, affinity chromatography on concanavalin A-Sepharose (Con A-Sepharose), and immunoaffinity chromatography. Elution profile from gel filtration showed three peaks in both cases, peak I and II were clearly separated in murrel but not in carp. Peak II demonstrated strong GtH activity in both murrel and carp but this activity could also be detected in peak I and III of carp. TSH activity was restricted to peak I in murrel and was distributed in all three peaks in carp. Chromatography on Con A-Sepharose was useful in harvesting carp glycoprotein hormones, but gave no advantage in murrel. A pure homogenous GtH from murrel and carp could be obtained by using immunoaffinity chromatography. Polyacrylamide gel electrophoresis of murrel and carp GtH showed a single discrete band. Determination of molecular weight (MW) by Sephadex G-100 gel filtration indicated that murrel and carp GtH were 42,000 and 40,000 Da, respectively. SDS-polyacrylamide gel electrophoresis of murrel and carp GtH revealed two dissimilar subunits, α and β. MW of murrel and carp α-subunits were 18,000 and 16,000 while those of β were 27,000 and 26,000 Da, respectively. Comparison of electrophoretic patterns of murrel and carp GtH α and β with ovine LH subunits reveal distinct teleostean GtH subunits.