Pseudo-enzymatic hydrolysis of 4-nitrophenyl myristate by human serum albumin

Paolo Ascenzi, Mauro Fasano

Research output: Contribution to journalArticlepeer-review

Abstract

Most of the esterase properties of human serum albumin (HSA) are the result of multiple irreversible chemical modifications rather than turnover. The HSA-catalyzed hydrolysis of 4-nitrophenyl myristate (NphOMy) is consistent with the minimum three-step mechanism involving the acyl-enzyme intermediate HSA-OMy: Under all the experimental conditions, values of K s (= k -1/k +1), k +2, and k +2/K s determined under conditions where [HSA]≥5×[NphOMy] and [NphOMy]≥5×[HSA] match very well each other. The deacylation process is rate limiting in catalysis (i.e., k +3≪k +2) and k -2~k -3~0s -1. The pH dependence of k +2/K s, k +2, and K s reflects the acidic pK a-shift of one ionizing group from 8.9±0.2 in NphOMy-free HSA to 6.8±0.3 in the HSA:NphOMy adduct. The HSA-catalyzed hydrolysis of NphOMy is inhibited competitively by diazepam, indicating that Tyr411 is the active-site nucleophile.

Original languageEnglish
Pages (from-to)219-223
Number of pages5
JournalBiochemical and Biophysical Research Communications
Volume422
Issue number2
DOIs
Publication statusPublished - Jun 1 2012

Keywords

  • 4-Nitrophenyl myristate
  • AMPSO
  • Bis-Tris
  • Hepes
  • HSA
  • Human serum albumin
  • MyOH
  • NphOH
  • NphOMy
  • PH effects
  • Pseudo-enzymatic hydrolysis

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology
  • Molecular Biology

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