Inhibition of rabbit intestinal brush border sucrase by indolin 2,3-dione (isatin) at pH 5.0.
Isatin (10 mM) inhibited the activity of rabbit brush border sucrase by 60% at pH 5.0 but it had no effect on enzyme activity around neutral pH. Isatin inhibition of sucrase was unaffected by Na+ ions but K+ and Cs+ ions reduced enzyme inhibition, partially. Kinetic analysis revealed that sucrase inhibition by isatin at acidic pH was non-competitive with Ki of the order 6.5-7.8 mM. Isatin together with 4 mM harmaline or iodoacetate (3 mM) or dithionitrobenzene (2 mM) yielded 80-85% inhibition of the enzyme. These observations suggest that inhibitory sites for isatin, harmaline and -SH group reacting agents are distinct in rabbit brush border sucrase.
Department of Biochemistry, Panjab University, Chandigarh.
M L
ML
Gargari
U
U
Siddiqui
R C
RC
Bansal
K
K
Singh
A
A
Mahmood
D000818:Animals; D006863:Hydrogen-Ion Concentration; D007422:Intestines / Q000201:enzymology* / Q000648:ultrastructure; D007510:Isatin / Q000378:metabolism*; D008871:Microvilli / Q000201:enzymology; D011817:Rabbits; D013393:Sucrase / Q000037:antagonists & inhibitors*
D007510:Isatin; D013393:Sucrase