AMINE OXIDASE ENZYMES OF SHEEP BLOOD-VESSELS AND BLOOD-PLASMA - A COMPARISON OF THEIR PROPERTIES

1. A comparison between the biochemical properties of semicarbazide-sensitive amine oxidase (SSAO) activities has been made in sheep blood plasma and arterial wall. 2. The metabolism of benzylamine (BZ) by blood plasma was resolved into high affinity (K(m) 2.76 +/- 0.24-mu-M) and low affinity (K(m) 743 +/- 49-mu-M) activities. Spermidine metabolism was by a single component (K(m) 174 +/- 22-mu-M) and this amine reduced the metabolism of high concentrations of BZ. 3. A single component metabolised BZ in arterial homogenates (K(m) 11.3 +/- 1.3-mu-M) and which metabolised spermidine at a very slow rate. 4. Dopamine was deaminated by plasma SSAO and competed with both low and high concentrations of BZ. Dopamine also interfered with arterial metabolism of BZ. 5. These results suggest that there are two SSAO enzymes in sheep blood plasma, with one having similar properties to SSAO in the arterial wall.