Topogenesis of carboxylesterases: a rat liver isoenzyme ending in -HTEHT-COOH is a secreted protein.
We have cloned a rat liver cDNA that encodes a carboxylesterase isoenzyme, as revealed by immunoprecipitation, cytochemical staining and inhibition by bis-p-nitrophenylphosphate of the product expressed in transfected COS cells. The predicted polypeptide ends in -HTEHT-COOH. The product is secreted by COS cells with a half-time of about 1 hour, after maturation of oligosaccharide chains in the Golgi complex. A variant ending in -HTEL-COOH is stable in the cells. This strengthens the existing evidence that the HXEL-COOH end signals proteins for retrieval from the secretory traffic in animal cells. The encoded enzyme still remains to be identified. It shows 98% homology to an esterase sequenced earlier (Takagi et al. 1988, J. Biochem. 104, 801-806; Long et al. 1988, Biochem. Biophys. Res. Commun. 156, 866-873); however it must be an enzyme from the serum, not from the microsomes.
Robbi
M
M
Laboratoire de Chimie Physiologique, Université de Louvain, Brussels, Belgium.
Beaufay
H
H
D000595:Amino Acid Sequence; D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D014644:Genetic Variation; D008862:Microsomes, Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D051381:Rats; D011919:Rats, Inbred Strains; D011994:Recombinant Proteins; D013997:Time Factors; D014162:Transfection
D011994:Recombinant Proteins; D002265:Carboxylic Ester Hydrolases