AMINE OXIDASE .15. SULFHYDRYL GROUPS OF BEEF LIVER MITOCHONDRIAL AMINE OXIDASE

Beef liver mitochondrial amine oxidase components 1 and 2 contain about 28 and 86 sulfhydryl groups per mole of enzyme or 7 sulfhydryl groups per 100,000 g of protein. The rate of reaction of p-chloromercuribenzoate with the enzyme was complete in about 30 min and 8 m urea had no effect on the rate of reaction. After reaction of all the sulfhydryl groups with p-chloromercuribenzoate, the enzyme was not completely inhibited and removal of the excess sulfhydryl reagent led to reactivation of the enzyme. At higher p-chloromercuribenzoate concentrations, the enzyme was inhibited noncompetitively. Iodoacetic acid and iodoacetamide did not inhibit the enzyme appreciably even at a concentration of 1 × 10-3 m. Certain heavy metal salts inhibited the enzyme noncompetitively. The sulfhydryl groups probably are required for conformational stability rather than being required for catalysis. © 1969.