Phosphopyridoxal complexes with histamine and histidine. ( 3) The influence of presumed complex on activity of rat intestinal histaminase. 
Histamine in high concentration inhibits the rat intestinal histaminase (diamine oxidase E.C. 1.4.3.6.).  The apparent Km is approximately 4.2 X 10(-5) M. This inhibition can be reversed by an addition of PLP.  It was also found that excess of PLP inhibits enzyme activity.  It is competitive inhibition.  Histamine and other amines which were associated with enzyme inhibition form spectrophotometricaly demonstrable complex with PLP.  The possible mechanism of the inhibitory action of PLP and complex with histamine and other amines on rat intestinal histaminase activity are discussed.