Biomaterial Database

Hydrolysis of pyrrolizidine alkaloids by guinea pig hepatic carboxylesterases. 1992

S R Dueker, and M W Lamé, and H J Segall

Department of Veterinary Pharmacology and Toxicology, University of California, Davis 95616.

Two carboxylesterases (GPL1 and GPH1) were isolated from guinea pig hepatic microsomes and assayed for activity using the following pyrrolizidine alkaloids (PAs): seneciphylline (SNP), monocrotaline (MCT), and a mixture of senecionine (SEN) and integerrimine (INT) referred to as SEN-INT. GPH1 was able to effect the hydrolysis of all PAs, however, only minimal activity was seen for SEN-INT. The specific activity of GPL1 for p-nitrophenyl acetate was four times that of GPH1, but the former showed no activity toward PAs. The molecular weights and pIs were determined for both enzymes, and the Michaelis-Menten constants for two PAs, SNP and MCT were obtained using GPH1. The response to inhibitors confirmed GPH1 as a type B serine hydrolase although it was also inhibited by HgCl2. The isolation of a PA active esterase from the guinea pig may help to explain the resistance of this animal to PA intoxication, while enzyme substrate specificity may explain how the guinea pig's susceptibility to PA intoxication can differ toward various PAs.

UI	MeSH Term	Description	Entries
D007527	Isoenzymes	Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.	Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008297	Male		Males
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D011763	Pyrrolizidine Alkaloids	A group of ALKALOIDS, characterized by a nitrogen-containing necine, occurring mainly in plants of the BORAGINACEAE; COMPOSITAE; and LEGUMINOSAE plant families. They can be activated in the liver by hydrolysis of the ester and desaturation of the necine base to reactive electrophilic pyrrolic CYTOTOXINS.	Pyrrolizidine Alkaloid,Senecio Alkaloid,Senecio Alkaloids,Alkaloid, Pyrrolizidine,Alkaloid, Senecio,Alkaloids, Pyrrolizidine,Alkaloids, Senecio
D002265	Carboxylic Ester Hydrolases	Enzymes which catalyze the hydrolysis of carboxylic acid esters with the formation of an alcohol and a carboxylic acid anion.	Carboxylesterases,Ester Hydrolases, Carboxylic,Hydrolases, Carboxylic Ester
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D006868	Hydrolysis	The process of cleaving a chemical compound by the addition of a molecule of water.
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia