ID   VSPAA_CERCE             Reviewed;          27 AA.
AC   Q9PRM8; Q9PRM9; Q9PRN0;
DT   10-JUL-2007, integrated into UniProtKB/Swiss-Prot.
DT   10-JUL-2007, sequence version 2.
DT   03-AUG-2022, entry version 48.
DE   RecName: Full=Snake venom serine protease Afaacytin alpha/beta/beta' chains;
DE            Short=SVSP;
DE            EC=3.4.21.-;
DE   Flags: Fragment;
OS   Cerastes cerastes (Horned desert viper).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Viperidae; Viperinae; Cerastes.
OX   NCBI_TaxID=8697;
RN   [1]
RP   PROTEIN SEQUENCE, FUNCTION, ACTIVITY REGULATION, AND SUBUNIT.
RC   TISSUE=Venom;
RX   PubMed=8521839; DOI=10.1111/j.1432-1033.1995.756_3.x;
RA   Laraba-Djebari F., Martin-Eauclaire M.-F., Mauco G., Marchot P.;
RT   "Afaacytin, an alpha beta-fibrinogenase from Cerastes cerastes (horned
RT   viper) venom, activates purified factor X and induces serotonin release
RT   from human blood platelets.";
RL   Eur. J. Biochem. 233:756-765(1995).
CC   -!- FUNCTION: Snake venom serine protease that exhibits alpha-fibrinase and
CC       beta-fibrinogenase activities. It replaces missing factors VIII (F8)
CC       and IX (F9) in deficient plasmas by activating purified human factor X
CC       (F10) into factor Xa. It releases serotonin from platelets and induces
CC       platelet aggregation in human (but not in rabbit). Has caseinolytic,
CC       arginine-esterase and amidase activities. {ECO:0000269|PubMed:8521839}.
CC   -!- ACTIVITY REGULATION: Inhibited by diisopropylfluorophosphate (DFP),
CC       benzamidine, heparin and hirudin, but not by plasmatic thrombin
CC       inhibitors, antithrombin-III and ecotin. {ECO:0000269|PubMed:8521839}.
CC   -!- SUBUNIT: Heterodimer of an alpha and a beta chain. Subunit beta is
CC       constituted of two disulfide-linked polypeptidic chains, beta and
CC       beta'. Calcium appears to be required for structural cohesion of the
CC       molecule. {ECO:0000269|PubMed:8521839}.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland.
CC   -!- PTM: Both chains alpha and beta are N-glycosylated.
CC   -!- SIMILARITY: Belongs to the peptidase S1 family. Snake venom subfamily.
CC       {ECO:0000255|PROSITE-ProRule:PRU00274}.
CC   -!- CAUTION: As the three chains have the same N-terminal sequence, they
CC       are merged. The respective apparent molecular mass of the chains are
CC       43000 (alpha), 35500 (beta) and 10200 (beta') as determined by SDS/PAGE
CC       under reducing conditions. {ECO:0000305}.
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DR   PIR; S63486; S63486.
DR   PIR; S63487; S63487.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0008236; F:serine-type peptidase activity; IEA:UniProtKB-KW.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   GO; GO:0006508; P:proteolysis; IEA:UniProtKB-KW.
PE   1: Evidence at protein level;
KW   Blood coagulation cascade activating toxin; Direct protein sequencing;
KW   Disulfide bond; Fibrinogenolytic toxin; Fibrinolytic toxin; Glycoprotein;
KW   Hemostasis impairing toxin; Hydrolase;
KW   Platelet aggregation activating toxin; Protease; Secreted; Serine protease;
KW   Toxin.
FT   CHAIN           1..>27
FT                   /note="Snake venom serine protease Afaacytin
FT                   alpha/beta/beta' chains"
FT                   /id="PRO_0000294993"
FT   DOMAIN          1..>27
FT                   /note="Peptidase S1"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00274"
FT   DISULFID        7..?
FT   NON_TER         27
SQ   SEQUENCE   27 AA;  2918 MW;  7CA3BE584BFEB0AF CRC64;
     VIGGAECNIN EHRSLVLLYX SSSXFGE