Studies of rabbit brain, intestine and liver guanine aminohydrolase

Guanine aminohydrolase (EC 3.5.4.3) from rabbit brain, intestine, and liver has been purified to homogeneity by affinity chromatography at room temperature and 0-4 degrees C. In all cases the recovery and fold purification was greatest for purification at room temperature. Each enzyme has a subunit mol. wt of 49,500 and crosslinking studies revealed the native form to be a dimer. The amino acid analysis showed a high content of asx, glx, ser, gly and leu; the pI was 5.0 for each prep. The Michaelis constants at pH 8.0 were 6.1, 6.1 and 5.8 X 10(-6) M for brain, intestine and liver GAH respectively. The enzymes had a broad pH activity profile with an optimum of pH 8.0-8.5.