Abstract
Effects of detergents, especially sodium dodecyl sulfate (SDS) and sodium taurocholate (NaTC), on some lipases were studied.
The lipase preparations used were hog pancreas lyophilized powder (PL), pseudomonas lipase (PsL) and candida cylindracea. lipase (CL).
Lipolytic activity was determined by estimation of liberated fatty acids, using tributyrin as a substrate, by pH-stat titration with 0.005N sodium hydroxide at 25°.
The pH optima were 8.0 to PL and 7.5 to PsL and CL. Inhibitions of lipolytic activities were observed at all concentrations used of SDS and NaTC, and shifting of pH optimum was not seen for all combinations except for PsL-NaTC. Inhibition by SDS or NaTC was smaller in case of CL than in others, and they were almost the same in cases of PL and PsL.
To investigate in detail inhibition of lipolytic activity, kinetic studies for the amounts of substrate were performed. With Lineweaver-Burk's plots, the types of inhibition by SDS or NaTC were miscellaneous, especially NaTC acted on PL as a noncompetitive inhibitor, on PsL as an un-competitive one, and on CL as mixed one. In case of CL, SDS inhibited lipolytic activity un-competitively in concentrations below 300μM, and competitively in concentrations higher than 400μM.
Interesting results were obtained by using coexistence of SDS with NaTC. With regard to lipolysis catalyzed by the three lipases, the inhibitory rate b coexistence with these two detergents was smaller than those by each detergent used separately. NaTC was unable to reverse the inhibition to the rate in the complete system in the presence of SDS on lipolysis. On the contrary, the reverse by SDS was complete in the presence of NaTC.
