PEPTIDASE ACTIVITY IN LEUCOCYTES, ERYTHROCYTES AND PLASMA OF YOUNG ADULT AND SENILE SUBJECTS 12

Abstract

The hydrolysis of glycylglycylglycine (GGG) by human plasma, erythrocytes, and leucocytes was measured with the micro-technic of Grassmann and Heyde. The rate of hydrolysis is constant in all 3 constituents until about 70% of the tripeptide is split and is proportional to enzyme concn. Hydrolysis is activated by Co, inhibited by Mg and Mn, and is optimal aroung pH 7.1. Hydrolysis increases with increase in temp. up to 48[degree]C, and becomes inactivated rapidly at higher temps. The similar characteristics of hydrolysis of GGG make it likely that the same enzyme mechanism is involved in plasma, erythrocytes, and leucocytes. Per unit vol., red blood cells of young adults are over 100 times as active as plasma, white blood cells of young adults nearly 500 times as active as plasma. Per unit cell, the activity of leucocytes from young people is about 40 times greater than that of erythrocytes. The avg. rate of hydrolysis of GGG by leucocytes is significantly higher (about 70%) in senile people (67-90 yrs.) than in young people (21-32 yrs.). On the other hand, no significant increase in rate of hydrolysis by plasma or erythrocytes of old people was observed.