Guinea‐pig liver leukotriene A4 hydrolase

Abstract
Leukotriene A4 hydrolase from perfused guinea-pig liver was purified 1200-fold to near homogeneity with a yield of about 20%. Apparent values of Km and Vmax at 37.degree. C (27 .mu.M and 68 .mu.mol .times. mg-1), turnover number, and activation energy for the conversion of leukotriene A4 into leukotriene B4 were estimated from kinetic data obtained at -10.degree. C, 0.degree. C (Arrhenius plots). Physical properties including Mr (67,000-71,000), pH optimum, isoelectric point and Stokes'' radius were determined. The amino acid composition and N-terminal amino acid sequence were established after carboxymethylation of the enzyme. Unlike liver cytosolic epoxide hydrolase, the purified enzyme did not catalyze the conversion of leukotriene A4 into (5S,6R)-5,6-dihydoxy-7,9-trans-11,14-cis-icosatetraenoic acid.

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