Lipoprotein lipase catalyzed hydrolysis of water-soluble p-nitrophenyl esters. Inhibition by apolipoprotein C-II

Biochemistry. 1982 Dec 21;21(26):6872-9. doi: 10.1021/bi00269a038.

Abstract

Bovine milk lipoprotein lipase (LpL) catalyzes the hydrolysis of the water-soluble esters p-nitrophenyl acetate (PNPA) and p-nitrophenyl butyrate (PNPB). The same protein and same active site are involved in hydrolysis of water-soluble p-nitrophenyl esters and emulsified trioleoylglycerol since (a) trioleoylglycerol hydrolysis and PNPB hydrolysis activities coelute from the heparin-Sepharose affinity column used to purify LpL and (b) LpL-catalyzed hydrolyses of trioleoylglycerol and PNPB are inhibited to equal extents by phenylmethanesulfonyl fluoride. The effect of apolipoprotein C-II (apoC-II) on the LpL-catalyzed hydrolysis of PNPA and PNPB has been determined. ApoC-II inhibits hydrolysis of both esters, with a maximum extent of inhibition of 70-90%. Inhibition of the LpL-catalyzed hydrolysis of PNPB is specific for apoC-II, since apolipoproteins A-I, C-I, and C-III-2 have little effect on this reaction, and is partial noncompetitive in form. KI values for apoC-II inhibition of the LpL-catalyzed hydrolysis of PNPA and PNPB are in the range 0.26-0.83 microM. The effect of apoC-II on the temperature dependences of LpL-catalyzed hydrolysis of both esters and on NaCl inhibition of LpL-catalyzed PNPB hydrolysis is consistent with a change in rate-determining step with LpL and apoC-II interact. These results indicate not only that there is an interaction between apoC-II and LpL in aqueous solution in the absence of a lipid interface but also that this interaction conformationally modulates the active site of the enzyme.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Apolipoprotein C-II
  • Apolipoproteins / pharmacology*
  • Apolipoproteins C*
  • Cattle
  • Hydrolysis
  • Lipoprotein Lipase / metabolism*
  • Mathematics
  • Nitrophenols / metabolism*
  • Time Factors

Substances

  • Apolipoprotein C-II
  • Apolipoproteins
  • Apolipoproteins C
  • Nitrophenols
  • 4-nitrophenyl acetate
  • Lipoprotein Lipase