Signal peptidase I

{{Infobox enzyme

| Name = Signal peptidase I

| EC_number = 3.4.21.89

| CAS_number = 65979-36-4

| GO_code =

| image =

| width =

| caption =

}}

Signal peptidase I ({{EC number|3.4.21.89}}, leader peptidase I, signal proteinase, Escherichia coli leader peptidase, eukaryotic signal peptidase, eukaryotic signal proteinase, leader peptidase, leader peptide hydrolase, leader proteinase, signal peptidase, pilin leader peptidase, SPC, prokaryotic signal peptidase, prokaryotic leader peptidase, HOSP, prokaryotic signal proteinase, propeptidase, PuIO prepilin peptidase, signal peptide hydrolase, signal peptide peptidase, signalase, bacterial leader peptidase 1) is an enzyme.{{cite journal | vauthors = Black MT | title = Evidence that the catalytic activity of prokaryote leader peptidase depends upon the operation of a serine-lysine catalytic dyad | journal = Journal of Bacteriology | volume = 175 | issue = 16 | pages = 4957–61 | date = August 1993 | pmid = 8394311 | pmc = 204959 | doi = 10.1128/jb.175.16.4957-4961.1993 }}{{cite journal | vauthors = Nunnari J, Fox TD, Walter P | title = A mitochondrial protease with two catalytic subunits of nonoverlapping specificities | journal = Science | volume = 262 | issue = 5142 | pages = 1997–2004 | date = December 1993 | pmid = 8266095 | doi = 10.1126/science.8266095 }}{{cite journal | vauthors = Tschantz WR, Sung M, Delgado-Partin VM, Dalbey RE | title = A serine and a lysine residue implicated in the catalytic mechanism of the Escherichia coli leader peptidase | journal = The Journal of Biological Chemistry | volume = 268 | issue = 36 | pages = 27349–54 | date = December 1993 | pmid = 8262975 }}{{cite book | vauthors = Lively MO, Newsome AL, Nusier M | title = Eukaryote microsomal signal peptidases | series = Methods in Enzymology | volume = 244 | pages = 301–14 | date = 1994 | pmid = 7845216 | doi = 10.1016/0076-6879(94)44024-7 }}{{cite book | vauthors = Tschantz WR, Dalbey RE | title = Bacterial leader peptidase 1 | series = Methods in Enzymology | volume = 244 | pages = 285–301 | date = 1994 | pmid = 7845215 | doi = 10.1016/0076-6879(94)44023-9 }}{{cite journal | vauthors = Chaal BK, Mould RM, Barbrook AC, Gray JC, Howe CJ | title = Characterization of a cDNA encoding the thylakoidal processing peptidase from Arabidopsis thaliana. Implications for the origin and catalytic mechanism of the enzyme | journal = The Journal of Biological Chemistry | volume = 273 | issue = 2 | pages = 689–92 | date = January 1998 | pmid = 9422718 | doi = 10.1074/jbc.273.2.689 | doi-access = free }}{{cite journal | vauthors = Inoue K, Baldwin AJ, Shipman RL, Matsui K, Theg SM, Ohme-Takagi M | title = Complete maturation of the plastid protein translocation channel requires a type I signal peptidase | journal = The Journal of Cell Biology | volume = 171 | issue = 3 | pages = 425–30 | date = November 2005 | pmid = 16275749 | pmc=2171254 | doi = 10.1083/jcb.200506171 | url = http://orca.cf.ac.uk/64414/1/200506171.pdf | doi-access = free }} This enzyme catalyses the following chemical reaction

: Cleavage of hydrophobic, N-terminal signal or leader sequences

This enzyme is present in bacterial membranes and in chloroplast thylakoid membranes.