Abstract
1) Guanase activities in blood from 120 subjects were determined by measuring the radioactivity of 14C-uric acid derived from 14C-guanine.This method was able to determine the guanase activity less than 0.1 unit/l.
2) The normal range of guanase activity in serum was 0.2-0.8unit/l.
3) A correlation coefficient between the method which determine the ammonia released from 8-azaguanine by guanase colorimetrically and the method using radiolabelled substrate was 0.994, and thus it was shown that ammonia method is highly reliable in measuring the serum guanase activity of the normal range.
