Mechanism of inhibition of LDL phospholipase A2 by monocyclic-beta-lactams. Burst kinetics and the effect of stereochemistry

Biochemistry. 1998 Jul 14;37(28):10087-93. doi: 10.1021/bi9801412.


Investigation of the inhibition of LDL-associated phospholipase A2 by monocyclic beta-lactams has shown that LDL phospholipase A2 is capable of hydrolyzing monocyclic-beta-lactams by a mechanism which shares many similarities to the hydrolysis of beta-lactams by beta-lactamases. We believe that this is the first demonstration of a serine-dependent lipase being able to hydrolyze an amide bond. Although 4-(phenylthio)-N-(4-phenyl-2-oxobutyl)azetidin-2-one, SB-216477, and its enantiomers are relatively modest covalent inactivators with kobs/[I] = 46 M-1 s-1 for the R enantiomer, analysis of the kinetics of inactivation and reactivation shows that these compounds act as slow-turnover substrates, presumably via an acylation-deacylation mechanism. The detection of a suprastoichiometric burst indicates that the pathway must be branched with the branching giving rise to the slow reactivation via a more stable covalent intermediate. Study of the two enantiomers of SB-216477 shows that LDL-associated phospholipase A2 is sensitive to the beta-lactam stereochemistry at C4. However, a common achiral intermediate is formed along the turnover pathway, and this must be at or immediately prior to the branch point.

MeSH terms

  • 1-Alkyl-2-acetylglycerophosphocholine Esterase
  • Azetidines / metabolism
  • Azetidines / pharmacology*
  • Chromatography, High Pressure Liquid
  • Enzyme Activation / drug effects
  • Kinetics
  • Lactams*
  • Lipoproteins, LDL / metabolism*
  • Phospholipases A / antagonists & inhibitors*
  • Phospholipases A / metabolism
  • Phospholipases A2
  • Spectrum Analysis
  • Stereoisomerism
  • Substrate Specificity
  • beta-Lactams / metabolism
  • beta-Lactams / pharmacology*


  • Azetidines
  • Lactams
  • Lipoproteins, LDL
  • SB-216477
  • beta-Lactams
  • Phospholipases A
  • Phospholipases A2
  • 1-Alkyl-2-acetylglycerophosphocholine Esterase