Bile salt modulated stereoselection in the cholesterol esterase catalyzed hydrolysis of .alpha.-tocopheryl acetates

1991 ◽  
Vol 113 (7) ◽  
pp. 2797-2799 ◽  
Author(s):  
H. A. Zahalka ◽  
P. J. Dutton ◽  
B. O'Doherty ◽  
T. A. M. Smart ◽  
J. Phipps ◽  
...  
Keyword(s):  
Bile Salt ◽  
Cholesterol Esterase ◽  
Hydrolysis Of

scholarly journals Lipoamidase activity in normal and mutagenized pancreatic cholesterol esterase (bile salt-stimulated lipase)

1993 ◽  
Vol 291 (1) ◽  
pp. 65-69 ◽  
Author(s):  
D Y Hui ◽  
K Hayakawa ◽  
J Oizumi
Keyword(s):  
Enzyme Activity ◽  
Gastrointestinal Tract ◽  
Recombinant Protein ◽  
Human Milk ◽  
Bile Salt ◽  
Enzyme Kinetics ◽  
Cholesterol Esterase ◽  
Amide Hydrolysis ◽  
Ester Linkage ◽  
Hydrolysis Of

Purified human milk lipoamidase was digested with endoproteinase Lys-C and the digested peptides were subjected to gasphase microsequence analysis. The sequencing of three isolated peptides of human milk lipoamidase revealed the identity of this protein with human milk bile salt-stimulated lipase (pancreatic cholesterol esterase). The identity of the cholesterol esterase with lipoamidase was confirmed by expressing a recombinant form of rat pancreatic cholesterol esterase and testing for lipoamidase activity of the recombinant protein. The results showed that the recombinant cholesterol esterase displayed both lipolytic and lipoamidase activities and was capable of hydrolysing triacetin and lipoyl-4-aminobenzoate (LPAB). The mechanisms of the esterase and amidase activities of the enzyme were further tested by determining enzyme activity in a mutagenized cholesterol esterase with a His435-->Gln435 substitution. This mutation has been shown previously to abolish enzyme activity against esterase substrates [DiPersio, Fontaine and Hui (1991) J. Biol. Chem. 266, 4033-4036]. We showed that the mutagenized protein was effective in hydrolysing the amidase substrate LPAB and displayed similar enzyme kinetics to those of the native enzyme. These data indicate that the mechanism for the cholesterol esterase hydrolysis of lipoamides is different from that of the hydrolysis of substrates with an ester linkage. The presence of an enzyme in the gastrointestinal tract capable of both ester and amide hydrolysis suggests an important role for this protein in the digestion and absorption processes.

Bile Salt-Modulated Stereoselection in the Cholesterol Esterase-Catalyzed Hydrolysis of .alpha.-Tocopherol Acetates

1995 ◽  
Vol 117 (21) ◽  
pp. 5677-5686 ◽  
Author(s):  
A. Moore ◽  
P. J. Dutton ◽  
H. A. Zahalka ◽  
G. W. Burton ◽  
K. U. Ingold
Keyword(s):  
Bile Salt ◽  
Alpha Tocopherol ◽  
Cholesterol Esterase ◽  
Hydrolysis Of

scholarly journals A simple method for the determination of the cholesterol esterase activity.

2013 ◽  
Vol 60 (3) ◽  
Author(s):  
Agnieszka Ewa Stępień ◽  
Mykhailo Gonchar
Keyword(s):  
Human Serum ◽  
Esterase Activity ◽  
Cholesterol Oxidase ◽  
Cholesterol Esterase ◽  
Cholesterol Esters ◽  
Simple Method ◽  
Bacterial Enzyme ◽  
Low Costs ◽  
Hydrolysis Of

The proposed method determines the activity of cholesterol esterase (CEH) and takes advantage of its ability to catalyze the hydrolysis of cholesterol esters naturally present in human serum. The assay is based on Allain's method of spectrophotometric determination of cholesterol by means of cholesterol oxidase, peroxidase, but using 3,5-dichloro-dihydroxybenzenesulfonic acid (DHBS) as phenolic chromogen and human serum as a source of substrate for the CEH as a novelty. Furthermore, it is characterized by low costs and high precision. It can be employed to control the activity of CE preparations used for the preparation of enzymatic kits for the determination of cholesterol or for screening of potential bacterial enzyme producers.

Studies in Bile Salt Solutions. XIV. Electronic, Charge and Steric Substrate-Effects on the Esterase Activity of Bile-Salt-Stimulated Human Milk Lipase. Hydrolysis of 4-Substituted Phenyl Propionates

1986 ◽  
Vol 39 (2) ◽  
pp. 259 ◽  
Author(s):  
CJ Oconnor ◽  
ASH Mitha
Keyword(s):  
Human Milk ◽  
Bile Salt ◽  
Active Site ◽  
Esterase Activity ◽  
Electronic Charge ◽  
Electronic Interaction ◽  
Lipase Hydrolysis ◽  
Rate Determining Step ◽  
Esterolytic Activity ◽  
Hydrolysis Of

The rate constants of hydrolysis of a series of 4-substituted phenyl propionates, catalysed by bile-salt-stimulated human milk lipase in the absence and presence of cholate or taurocholate stimulation, have been measured at pH 7.3, 310.5 K. There is little evidence for an alkyl site electronic interaction in the rate-determining step of the esterolytic reaction. However, a negatively charged substrate or an amido-substituent caused an inhibition of unstimulated esterase activity. In the presence of the bile-salt cofactors, esterolytic activity against charged substrates may be stimulated or inhibited, depending on the proximity of the charge to the steroidal side chain and the subsequent substrate-interaction within the surrounding environment of the active site. It has been confirmed that bile-salt- stimulated lipase is not an amidase , but that an amide, of the correct geometry, may occupy the active site and restrict esterase activity.

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