title: A novel angiotensin I-converting enzyme mutation (S333W) impairs N-domain enzymatic cleavage of the anti-fibrotic peptide, AcSDKP.
abstract: BACKGROUND
  Angiotensin I-converting enzyme (ACE) has two functional N- and C-domain active centers that display differences in the metabolism of biologically-active peptides including the hemoregulatory tetrapeptide, Ac-SDKP, hydrolysed preferentially by the N domain active center. Elevated Ac-SDKP concentrations are associated with reduced tissue fibrosis.
  
  
  RESULTS
  We identified a patient of African descent exhibiting unusual blood ACE kinetics with reduced relative hydrolysis of two synthetic ACE substrates (ZPHL/HHL ratio) suggestive of the ACE N domain center inactivation. Inhibition of blood ACE activity by anti-catalytic mAbs and ACE inhibitors and conformational fingerprint of blood ACE suggested overall conformational changes in the ACE molecule and sequencing identified Ser333Trp substitution in the N domain of ACE. In silico analysis demonstrated S333W localized in the S1 pocket of the active site of the N domain with the bulky Trp adversely affecting binding of ACE substrates due to steric hindrance. Expression of mutant ACE (S333W) in CHO cells confirmed altered kinetic properties of mutant ACE and conformational changes in the N domain. Further, the S333W mutant displayed decreased ability (5-fold) to cleave the physiological substrate AcSDKP compared to wild-type ACE.
  
  
  CONCLUSIONS
  A novel Ser333Trp ACE mutation results in dramatic changes in ACE kinetic properties and lowered clearance of Ac-SDKP. Individuals with this mutation (likely with significantly increased levels of the hemoregulatory tetrapeptide in blood and tissues), may confer protection against fibrosis.
authors: Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America ; Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors: Sergei M
authors: SM
authors: Danilov
authors: Institute for Personalized Respiratory Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors: Michael S
authors: MS
authors: Wade
authors: Institute of Infectious Disease and Molecular Medicine and Division of Medical Biochemistry, University of Cape Town, Cape Town, South Africa.
authors: Sylva L
authors: SL
authors: Schwager
authors: Institute of Infectious Disease and Molecular Medicine and Division of Medical Biochemistry, University of Cape Town, Cape Town, South Africa.
authors: Ross G
authors: RG
authors: Douglas
authors: Department of Dermatology, Rush University, Chicago, Illinois, United States of America.
authors: Andrew B
authors: AB
authors: Nesterovitch
authors: Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, United States of America.
authors: Isolda A
authors: IA
authors: Popova
authors: Department of Medicine, University of Chicago, Chicago, Illinois, United States of America.
authors: Kyle D
authors: KD
authors: Hogarth
authors: Department of Medicine, University of Chicago, Chicago, Illinois, United States of America.
authors: Nakul
authors: N
authors: Bhardwaj
authors: Department of Anesthesiology, University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors: David E
authors: DE
authors: Schwartz
authors: Institute of Infectious Disease and Molecular Medicine and Division of Medical Biochemistry, University of Cape Town, Cape Town, South Africa.
authors: Edward D
authors: ED
authors: Sturrock
authors: Department of Medicine, University of Arizona, Tucson, Arizona, United States of America.
authors: Joe G N
authors: JG
authors: Garcia
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D003412:Cricetulus; D005355:Fibrosis / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009842:Oligopeptides / Q000235:genetics* / Q000378:metabolism*; D010455:Peptides / Q000235:genetics* / Q000378:metabolism; D007703:Peptidyl-Dipeptidase A / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D009842:Oligopeptides; D010455:Peptides; D007703:Peptidyl-Dipeptidase A; C058504:goralatide