Serine carboxypeptidase-like proteins

SHIRLEY, A.M., McMICHAEL, C.M., CHAPPLE, C The sng2 mutant of Arabidopsis is defective in the gene encoding the serine carboxypeptidase-like protein sinapoylglucose Choline sinapoyltransferase, Plant J., 2001, 28, 83-94. 

Shirley, A. M., and Chappie, C., 2003, Biochemical characterization of sinapoylglucose choline sinapoyltransferase, a serine carboxypeptidase-like protein that functions as an acyltransferase in plant secondary metabolism, J. Biol. Chem. 278 19870-19877. 

Lehfeldt, C., Shirley, A.M., Meyer, K., Ruegger, M.O., Gusumano, J.G., Viitanen, P.V., Strack, D. and Chappie, C. (2000) Cloning of the SNGl gene of Arabidopsis reveals a role for a serine carboxypeptidase-like protein as an acyltransferase in secondary metabolism. Plant Cell, 12,1295-306. 

There are two other examples for the recraitment of genes from primary metabolism. The homospermidine synthase from Senecio vernalis is derived from deoxyh T3usine synthase, an enzyme required for activation of translation factor 5A, and a serine carboxypeptidase-like protein that functions as an acyltransferase in secondary metabolism has been found in Arabidopsis thaliana. 

Li, A.X. and Steffens, J.C. (2000) An acyltrans-ferase catalyzing the formation of diacylglu-cose is a serine carboxypeptidase-like protein. Proc. Nad. Acad. Sci. USA 97, 6902-6907... 

Many secreted proteins, as well as smaller peptide hormones, are acted upon in the endoplasmic reticulum by tryptases and other serine proteases. They often cut between pairs of basic residues such as KK, KR, or RR.214-216 A substilisin-like protease cleaves adjacent to methionine.217 Other classes of proteases (e.g., zinc-dependent carboxypeptidases) also participate in this processing. Serine carboxypeptidases are involved in processing human prohormones.218 Among the serine carboxypeptidases of known structure is one from wheat219 and carboxypeptidase Y, a vacuolar enzyme from yeast.220 Like the pancreatic metallocarboxypeptidases discussed in Section 4, these enzymes remove one amino acid at a time, a property that has made carboxypeptidases valuable reagents for determination of amino acid sequences. Carboxypeptidases may also be used for modification of proteins by removal of one or a few amino acids from the ends. 

Proteases are essential for the conversion of inactive proprotein precursors into the active neuropeptides. Two main protease pathways have been elucidated for processing proneuropeptides and hormones the recently discovered cysteine protease cathepsin L with aminopeptidase B and the well-established subtilisin-like serine proteases that consist of prohormone con-vertases 1 and 2 followed by carboxypeptidase E/H. Endogenous regulators modulate these two protease pathways as endogenous peptide inhibitors, activators, and in vivo secretory vesicle proteins. Neuropeptides in CSE (cerebrospinal fluid) in neurological diseases can monitor brain nervous activity because neuropeptides represent active neurotransmission (93, 94). 

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