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Sheep tissue acetyl coenzyme A-dependent arylamine N-acetyltransferases

Acetyl coenzyme A-dependent arylamine N-acetyltransferases (NATs), EC 2.3.1.5. were measured in sheep tissues (N = 14) using p-aminobenzoic acid (PABA) as a substrate. Specific activities of liver, kidney, and lung NATs were 5.3 X 10(-3) +/- 1.4 (mean +/- SE) nmoles.min(-1).mg protein(-1), 3.4 X 10(-3) +/- 1.1 nmoles.min(-1).mg protein(-1), 2.5 X 10(-3) +/- 1.2 nmoles.min(-1).mg protein(-1), respectively. K-m values were 53 +/- 3 mu M for liver, 34 +/- 2 mu M for kidney, and 28 +/- 2 mu M for lung tissue. Optimum pH for the acetylation reaction was found as 7.5. The enzyme activity was stable for at least 6 months in all tissues, when stored at -70 degrees C. The enzyme from sheep tissues were quite heat stable. Inhibition studies showed that N-ethylmaleimide was a potent inhibitor of sheep tissue NAT enzymes. (C) 1997 Elsevier Science Inc.