Exposure of buffalo liver and kidney tissue arginases to a 150 w light source from a distance of 8-10 cm, in the presence of 0.05mM methylene blue, caused significant inhibition of arginase activity. It was determined that this inhibition occurred differently in liver and kidney tissues. Arginase activity was spectrophotometrically measured using the Thiosemicarbazide diacetyl-monoxime urea (TDMU) method. Following preincubation with MnCl2, exposure to a 150 w light source and the addition of methylene blue, the activity of arginase was found to be lower than that after preincubation with a 150 w light source and methylene blue and the addition of MnCl2. Addition of methylene blue to buffalo liver and kidney tissue did not reduce the activity of arginase when the enzymatic reaction was carried out in darkness or in daylight, indicating that arginase is subject to photoinactivation by methylene blue. Enzyme inhibition was reduced 45-48% to 63% in the liver tissue and 30-40% in the kidney tissue. The inhibitory effect of methylene blue on buffalo liver and kidney tissue of arginase and its kinetic properties were studied. The inhibition was found to be noncompetitive. Photoinactivation might show its effect by modifying imidazole groups of histidyl residues in arginase molecules.

Exposure of buffalo liver and kidney tissue arginases to a 150 w light source from a distance of 8-10 cm, in the presence of 0.05mM methylene blue, caused significant inhibition of arginase activity. It was determined that this inhibition occurred differently in liver and kidney tissues. Arginase activity was spectrophotometrically measured using the Thiosemicarbazide diacetyl-monoxime urea (TDMU) method. Following preincubation with MnCl2, exposure to a 150 w light source and the addition of methylene blue, the activity of arginase was found to be lower than that after preincubation with a 150 w light source and methylene blue and the addition of MnCl2. Addition of methylene blue to buffalo liver and kidney tissue did not reduce the activity of arginase when the enzymatic reaction was carried out in darkness or in daylight, indicating that arginase is subject to photoinactivation by methylene blue. Enzyme inhibition was reduced 45-48% to 63% in the liver tissue and 30-40% in the kidney tissue. The inhibitory effect of methylene blue on buffalo liver and kidney tissue of arginase and its kinetic properties were studied. The inhibition was found to be noncompetitive. Photoinactivation might show its effect by modifying imidazole groups of histidyl residues in arginase molecules.