Abstract: The inhibitive role of lanthanum ion on the arginase catalyzed hydrolysis of L-arginine was studied by microcalorimetry in a 40 mmol/L sodium barbiturate-hydrochloric acid buffer solution at 37 ℃ and pH of 9.4. The results indicated La3+ has remarkable inhibition effect on the catalytic activity of arginase and the inhibitory type belongs to the reversible noncompetitive inhibition with the inhibition constant of 2.74×10-4 mol/L. On the basis of the inhibition type and ion radius, we suggested that the binding site of La3+ to arginase is far from the active site of arginase.

Key words: arginase, lanthanum ion, reversible non-competitive inhibition, microcalorimetry