SIZE AND SHAPE OF TWO INTESTINAL DIPEPTIDASES

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Abstract
Physicochemical parameters were determined on glycyl-L-leucine hydrolase (glycyl-leucine dipeptidase, EC 3.4.13.2) and aminoacyl-L-proline hydrolase (proline dipeptidase, EC 3.4.13.9), purified from pig small intestine. The native MW were 115,000 and 113,000, respectively, as determined by a sedimentation equilibrium technique. Under denaturing conditions the MW were 51,000 and 63.200, respectively, using the same technique. Each dipeptidase is composed of 2 subunits of equal MW. The 2 dipeptidases have the same Stokes radius, 4.2 nm, analyzed by gel chromatography. The sedimentation coefficients were 5.8 S and 6.5 S and the intrinsic viscosities 5.4 ml/g and 5.8 ml/g, respectively. For both dipeptidases the measured physicochemical parameters are in accordance with the model of a prolate ellipsoid of revolution, having an axial ratio of about 5.