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.

Heat Stability of the Bile Salt-Stimulated Lipase in Human Milk Fortified with Sodium Taurocholate1

1988 ◽  
Vol 51 (4) ◽  
pp. 310-313 ◽  
Author(s):  
H. L. PAN ◽  
C. W. DILL ◽  
E. S. ALFORD ◽  
S. L. DILL ◽  
C. A. BAILEY ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Human Milk ◽  
Bile Salt ◽  
Lipase Activity ◽  
Sodium Taurocholate ◽  
Heat Stability ◽  
Heat Inactivation ◽  
Temperature Differential ◽  
Heat Stable ◽  
Control Samples

Time-temperature relationships for heat-inactivation of the bile salt-stimulated lipase activity were compared in whole human milk and in the same product fortified to 9 mM/ml with sodium taurocholate. Heat treatments were varied from 45 to 70°C for times ranging from 15s to 40 min. Enzyme activity was more heat stable in human milk fortified with taurocholate than in control samples. The temperature required for the onset of heat inactivation at 30-min holding time was increased from 45°C for control samples to 60°C following addition of taurocholate. A temperature differential of approximately 12°C was required in the fortified milks to produce inactivation equivalent to that observed in the control milks over the heating range studied.

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.

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

Studies in Bile Salt Solutions .XIII. Hydrophobic Substrate Effects on the Esterase Activity of Bile-Salt-Stimulated Human-Milk Lipase. Hydrolysis of 4-Nitrophenyl Alkanoates and Alkyl 4-Nitrobenzoates

1986 ◽  
Vol 39 (2) ◽  
pp. 249 ◽  
Author(s):  
CJ Oconnor ◽  
ASH Mitha ◽  
P Walde
Keyword(s):  
Human Milk ◽  
Bile Salt ◽  
Binding Site ◽  
Sodium Taurocholate ◽  
Sodium Cholate ◽  
Lipase Hydrolysis ◽  
Nitrobenzoic Acid ◽  
Hydrocarbon Chains ◽  
Hydrophobic Nature ◽  
Hydrolysis Of

The pseudo-first-order rate constants of hydrolysis of a series of 4-nitrophenyl alkanoates and a series of n-alkyl esters of 4-nitrobenzoic acid and of 4-nitrophenyl hexahydrobenzoate and cyclohexyl 4-nitrobenzoate, catalysed by bile-salt-stimulated human milk lipase in the absence and presence (2 mmol dm-3) of sodium cholate/cholic acid and sodium taurocholate , have been measured at pH 7.3, 310.5 K. It has been shown that the enzyme possesses a specific esterase acyl binding site which almost completely excludes the binding therein of a cyclohexyl group. There is also present a specific alkyl binding site which can fully accommodate a cyclohexyl ring. Both binding sites are hydrophobic in nature, but although the hydrophobic nature of the alkyl binding site is affected by bile-salt stimulation, that of the acyl site is not. Hydrophobicity parameters have been calculated for hydrocarbon chains lying in the acyl and alkyl binding positions of bile-salt-stimulated human milk lipase.

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

Bile-Salt-Stimulated Human Milk Lipase: Interaction with Proteins

1988 ◽  
Vol 3 (4) ◽  
pp. 390-402 ◽  
Author(s):  
Charmian J. O'Connor ◽  
Paul A.G. Butler ◽  
Bridget M. Sutton
Keyword(s):  
Human Milk ◽  
Bile Salt

THE HYDROLYSIS OF MONOPHOSPHOINOSITIDE BY EXTRACTS OF BRAIN

1967 ◽  
Vol 45 (6) ◽  
pp. 853-861 ◽  
Author(s):  
W. Thompson
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Calcium Ions ◽  
Brain Extract ◽  
Monovalent Cations ◽  
High Concentration ◽  
Diffusible Factor ◽  
Hydrolysis Of ◽  
The Brain ◽  
Long Chain

The hydrolysis of monophosphoinositide by soluble extracts from rat brain is described. Diglyceride and inositol monophosphate are liberated along with a small amount of free fatty acids. Hydrolysis of the lipid is optimal at pH 5.4 in acetate buffer. The reaction is stimulated by calcium ions or by high concentration of monovalent cations and, to a less extent, by long-chain cationic amphipathic compounds. Enzyme activity is lost on dialysis of the brain extract and can be restored by diffusible factor(s). Some differences in the conditions for hydrolysis of mono- and tri-phosphoinositides are noted.

scholarly journals Enzymatic hydrolysis of fumonisins in the gastrointestinal tract of broiler chickens

2017 ◽  
Vol 96 (12) ◽  
pp. 4342-4351 ◽  
Author(s):  
B Grenier ◽  
H E Schwartz-Zimmermann ◽  
C Gruber-Dorninger ◽  
I Dohnal ◽  
M Aleschko ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Enzymatic Hydrolysis ◽  
Broiler Chickens ◽  
Hydrolysis Of
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