SERPINA5 - Plasma serine protease inhibitor - human protein (Function)
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SERPINA5 »  Plasma serine protease inhibitor
Protein also known as:  Acrosomal serine protease inhibitor.
Gene name:  SERPINA5
Family name: Serpin
Entry whose protein(s) existence is based on evidence at protein level
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Heparin-dependent serine protease inhibitor acting in body fluids and secretions. Inactivates serine proteases by binding irreversibly to their serine activation site. Involved in the regulation of intravascular and extravascular proteolytic activities. Plays hemostatic roles in the blood plasma. Acts as a procoagulant and proinflammatory factor by inhibiting the anticoagulant activated protein C factor as well as the generation of activated protein C factor by the thrombin/thrombomodulin complex. Acts as an anticoagulant factor by inhibiting blood coagulation factors like prothrombin, factor XI, factor Xa, plasma kallikrein and fibrinolytic enzymes such as tissue- and urinary-type plasminogen activators. In seminal plasma, inactivates several serine proteases implicated in the reproductive system. Inhibits the serpin acrosin; indirectly protects component of the male genital tract from being degraded by excessive released acrosin. Inhibits tissue-and urinary-type plasminogen activator, prostate-specific antigen and kallikrein activities; has a control on the sperm motility and fertilization. Inhibits the activated protein C-catalyzed degradation of SEMG1 and SEMG2; regulates the degradation of semenogelin during the process of transfer of spermatozoa from the male reproductive tract into the female tract. In urine, inhibits urinary-type plasminogen activator and kallikrein activities. Inactivates membrane-anchored serine proteases activities such as MPRSS7 and TMPRSS11E. Inhibits urinary-type plasminogen activator-dependent tumor cell invasion and metastasis. May also play a non-inhibitory role in seminal plasma and urine as a hydrophobic hormone carrier by its binding to retinoic acid.  
  • CuratedUniProtKB
GO molecular function 
Acrosin bindingdefinition[GO:0032190]  
  • IPIUniProtKB
Glycosaminoglycan bindingdefinition[GO:0005539]  
  • TASUniProtKB
Heparin bindingdefinition[GO:0008201]  
  • TASUniProtKB
Phosphatidylcholine bindingdefinition[GO:0031210]  
  • IDAUniProtKB
Protease bindingdefinition[GO:0002020]  
  • IPIUniProtKB
Retinoic acid bindingdefinition[GO:0001972]  
  • IDAUniProtKB
Serine-type endopeptidase inhibitor activitydefinition[GO:0004867]  
  • IDAUniProtKB
GO biological process 
Fusion of sperm to egg plasma membranedefinition[GO:0007342]  
  • NASUniProtKB
Lipid transportdefinition[GO:0006869]  
  • IEAUniProtKB KW
Negative regulation of endopeptidase activitydefinition[GO:0010951] silver  
  • IBARefGenome
Negative regulation of proteolysisdefinition[GO:0045861] silver  
  • IEAOrtholog Compara
Regulation of proteolysisdefinition[GO:0030162] silver  
  • IBARefGenome
  • ISSOrtholog Curator
Enzymatic activity 
It is regulated in the following manner
Its inhibitory activity is greatly enhanced in the presence of glycosaminoglycans, heparin, thrombomodulin and phospholipids vesicles.  
  • CuratedUniProtKB
More information is available from:
According to KEGG, this protein belongs to the following pathway:
Complement and coagulation cascades  hsa04610+5104  


Biological process 
Fertilization  definition   [KW-0278]
Lipid transport  definition   [KW-0445]
Transport  definition   [KW-0813]
Molecular function 
Protease inhibitor  definition   [KW-0646]
Serine protease inhibitor  definition   [KW-0722]
Technical term 
Reference proteome  definition   [KW-1185]

Further external links

GeneWiki: Protein_C_inhibitor
GenomeRNAi: 5104
PRO: PR:P05154