Non-lipolytic and lipolytic sequence-related carboxylesterases: a comparative study of the structure-function relationships of rabbit liver esterase 1 and bovine pancreatic bile-salt-activated lipase.

To differentiate esterases from lipases at the structure-function level, we have compared the kinetic properties and structural features of sequence-related esterase 1 from rabbit liver (rLE) and bile-salt-activated lipase from bovine pancreas (bBAL). In contrast to rLE, bBAL hydrolyses water-insoluble medium and long chain esters as vinyl laurate, trioctanoin and olive oil. Conversely, rLE and bBAL are both active on water-soluble short chain esters as vinyl acetate, vinyl propionate, vinyl butyrate, tripropionin, tributyrin and p-nitrophenyl butyrate.

Use of an inhibitor to identify members of the hormone-sensitive lipase family.

Hormone-sensitive lipase (HSL) contributes importantly to the mobilization of fatty acids from the triacylglycerols stored in adipocytes, which provide the main source of energy in mammals. On the basis of amino acid sequence alignments and three-dimensional structures, this enzyme was previously found to be a suitable template for defining a family of serine carboxylester hydrolases. In this study, the HSL family members are characterized rather on the basis of their inhibition by 5-methoxy-3-(4-phenoxyphenyl)-3H-[1,3,4]oxadiazol-2-one (compound 7600).

Substrate specificity and kinetic properties of enzymes belonging to the hormone-sensitive lipase family: comparison with non-lipolytic and lipolytic carboxylesterases.

We have studied the kinetics of hydrolysis of triacylglycerols, vinyl esters and p-nitrophenyl butyrate by four carboxylesterases of the HSL family, namely recombinant human hormone-sensitive lipase (HSL), EST2 from Alicyclobacillus acidocaldarius, AFEST from Archeoglobus fulgidus, and protein RV1399C from Mycobacterium tuberculosis. The kinetic properties of enzymes of the HSL family have been compared to those of a series of lipolytic and non-lipolytic carboxylesterases including human pancreatic lipase, guinea pig pancreatic lipase related protein 2, lipases from Mucor miehei and Thermomyces lanuginosus, cutinase from Fusarium solani, LipA from Bacillus subtilis, porcine liver esterase and Esterase A from Aspergilus niger. Results indicate that human HSL, together with other lipolytic carboxylesterases, are active on short chain esters and hydrolyze water insoluble trioctanoin, vinyl laurate and olive oil, whereas the action of EST2, AFEST, protein RV1399C and non-lipolytic carboxylesterases is restricted to solutions of short chain substrates.

Distinction between esterases and lipases: a kinetic study with vinyl esters and TAG.

The better to characterize enzymes hydrolyzing carboxyl ester bonds (carboxyl ester hydrolases), we have compared the kinetic behavior of various lipases and esterases against solutions and emulsions of vinyl esters and TAG. Short-chain vinyl esters are hydrolyzed at comparable rates by esterases and lipases and have higher limits of solubility in water than corresponding TAG. Therefore, they are suited to study the influence of the physical state of the substrate on carboxyl ester hydrolase activity within a large concentration range.