Novel functions of human alpha(1)-protease inhibitor after S-nitrosylation: inhibition of cysteine protease and antibacterial activity

Biochem Biophys Res Commun. 2000 Jan 27;267(3):918-23. doi: 10.1006/bbrc.1999.2046.


alpha(1)-Protease inhibitor (alpha(1)PI), the most abundant serine protease inhibitor found in human plasma (at 30-60 microM), is a glycoprotein (53 kDa) having a single cysteine residue at position 232 (Cys(232)). We have found that Cys(232) of human alpha(1)PI was readily S-nitrosylated by nitric oxide (NO) without affecting inhibitory activity to trypsin or elastase. S-nitrosylated alpha(1)PI (S-NO-alpha(1)PI) not only retained inhibitory activity against these serine proteases, but also gained thiol protease inhibitory activity against a Streptococcus pyogenes protease; the parental alpha(1)PI did not have this activity. Furthermore, S-NO-alpha(1)PI exhibited bacteriostatic activity against Salmonella typhimurium at concentrations of 0.1-10 microM, which were 20- to 3000-fold stronger than those of the other NO-generating compounds or S-nitroso compounds such as S-nitrosoalbumin and S-nitrosoglutathione. NO appears to be transferred into the bacterial cells from S-NO-alpha(1)PI via transnitrosylation, as evidenced by electron spin resonance spectroscopy with an NO spin trap. Thus, we conclude that S-NO-alpha(1)PI may be generated from the reaction between alpha(1)PI and NO under inflammatory conditions, in which production of both is known to increase. As a result, new functions, i.e., antibacterial and thiol protease inhibitory activities of alpha(1)PI, were generated.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Cathepsin B / antagonists & inhibitors
  • Cattle
  • Cysteine
  • Cysteine Proteinase Inhibitors / pharmacology*
  • Electron Spin Resonance Spectroscopy
  • Humans
  • Kinetics
  • Liver / enzymology
  • Microbial Sensitivity Tests
  • Nitric Oxide / pharmacology*
  • Nitroso Compounds
  • Pancreatic Elastase / antagonists & inhibitors
  • Papain / antagonists & inhibitors
  • Salmonella typhimurium / drug effects
  • Thrombin / antagonists & inhibitors
  • Trypsin / metabolism
  • Trypsin Inhibitors / pharmacology
  • alpha 1-Antitrypsin / chemistry
  • alpha 1-Antitrypsin / pharmacology*


  • Anti-Bacterial Agents
  • Cysteine Proteinase Inhibitors
  • Nitroso Compounds
  • Trypsin Inhibitors
  • alpha 1-Antitrypsin
  • Nitric Oxide
  • Pancreatic Elastase
  • Trypsin
  • Thrombin
  • Cathepsin B
  • Papain
  • Cysteine