PMID: 2495022Apr 3, 1989Paper

Human milk bile-salt stimulated lipase: further investigations on the amino-acids residues involved in the catalytic site

Biochimica Et Biophysica Acta
N AbouakilD Lombardo

Abstract

The bile-salt-stimulated lipase purified from human skim milk was modified with diisopropyl phosphofluoridate (DFP), N-ethyl-5-phenylisoxazolium-3'-sulfonate and ethoxyformic anhydride. These chemical modifications lead to the following results: (1) the inhibition of the enzyme by DFP is due to the phosphorylation of a single residue, probably a serine residue, which may represent the acylable group of the enzyme; (2) carbethoxylation of histidine residues leads to inhibition of the enzyme activity. Among the nine modified histidine residues, only one is essential for enzyme activity; (3) a free carboxyl group with a pKa of 5.4 is also involved in catalysis. These three essential residues are involved in the enzymatic hydrolysis of substrates whatever their physical state (soluble or emulsified). Upon treatment with DFP as well as with ethoxyformic anhydride, the enzyme remains able to bind to the model interface formed by siliconized glass-beads with almost the same efficiency (Kd between 4.1 and 7.4.10(-8) M) than the native bile-salt-stimulated lipase (Kd = 6.3.10(-8) M). Moreover, the modified and native enzymes occupy the same interfacial area (4000-4600 A2/molecule). By contrast, the enzyme modified by N-ethyl-5-phenyliso...Continue Reading

References

Jan 1, 1974·Biochemistry·Y BursteinH Neurath
May 1, 1981·European Journal of Biochemistry·L Bläckberg, O Hernell
Jan 4, 1982·Biochimica Et Biophysica Acta·D Lombardo
Feb 1, 1982·The Journal of Clinical Investigation·C M MansbachR Verger
Sep 14, 1982·Biochimica Et Biophysica Acta·C Tiruppathi, K A Balasubramanian
Jun 15, 1981·Biochimica Et Biophysica Acta·D Lombardo, O Guy
Feb 12, 1981·Nature·B W DijkstraK H Kalk
Jan 1, 1972·Methods in Enzymology·A F Habeeb

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Citations

Mar 14, 1991·European Journal of Biochemistry·J D FourneronD Lombardo
Jan 15, 1991·Biochemistry·T BabaC S Wang
Mar 4, 1992·Biochimica Et Biophysica Acta·D R GjellesvikB T Walther

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