Studies on Leucine Aminopeptidase

概要

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In our previous report, a new method was presented for estimation of leucine aminopeptidase (LAP) by means of a direct colorimetric determination of ammonia reported by Fujii and Okuda. Leucin e amide was used for determination of LAP in our method. On the other hand, leucyl-β-naphthylamide was widely used for assay of this enzyme. LAP from various rat tissues and plasma was determined by using these substances as substrates. Tissue homogenates were sonicated and treated with Bromelain, followed by centrifugation for 60 min (105,000×g, at 4°C). The resultant supernatant was used for enzyme solution. Bromelain treatment caused solubilization of LAP from rat liver from its precipitate fraction, which was proved to exist by gel filtration on Sephadex G-200 column. TEAE-cellulose column chromatography and isoelectric focusing of LAP from various tissues provide an evidence that there exists this enzyme various forms characteristic to each tissue. It was demonstrated that various rat tissues contained several fractions which showed different substrate specificities to leucine amide and leucyl-β-naphthylamide. It was also clarified that the LAP elevated in plasma of CCl4 treated rats contained several fractions which showed different substrate specificities to leucine amide and leucyl-β-naphthylamide.
Japan Society of Clinical Chemistryの論文