Penicillin acylases as amidohydrolases and acyl transfer catalysts

1981 ◽  
Vol 3 (3) ◽  
pp. 112-117 ◽  
Author(s):  
J. Konecny
Keyword(s):  
Acyl Transfer ◽  
Penicillin Acylases

Kinetics and mechanism of acyl transfer by penicillin acylases

1983 ◽  
Vol 25 (2) ◽  
pp. 451-467 ◽  
Author(s):  
Jan Konecny ◽  
Andr� Schneider ◽  
Meinrad Sieber
Keyword(s):  
Kinetics And Mechanism ◽  
Acyl Transfer ◽  
Penicillin Acylases

Kinetics and mechanism of acyl transfer by penicillin acylases

1981 ◽  
Vol 3 (9) ◽  
pp. 507-512 ◽  
Author(s):  
J. Konecny ◽  
M. Sieber ◽  
A. Schneider
Keyword(s):  
Kinetics And Mechanism ◽  
Acyl Transfer ◽  
Penicillin Acylases

scholarly journals The relation of acyl transfer to the overall reaction of thiolase I from porcine heart.

1981 ◽  
Vol 256 (14) ◽  
pp. 7371-7377
Author(s):  
H.F. Gilbert ◽  
B.J. Lennox ◽  
C.D. Mossman ◽  
W.C. Carle
Keyword(s):  
Acyl Transfer ◽  
Porcine Heart

A Density Functional Theory Study on the Ring-Opening Polymerization of D-Lactide Catalyzed by a Bifunctional-Thiourea Catalyst

2009 ◽  
Vol 62 (2) ◽  
pp. 157 ◽  
Author(s):  
Rong-Xiu Zhu ◽  
Ruo-Xi Wang ◽  
Dong-Ju Zhang ◽  
Cheng-Bu Liu
Keyword(s):  
Density Functional Theory ◽  
Ring Opening ◽  
Density Functional ◽  
Population Analysis ◽  
Density Functional Theory Calculations ◽  
Ring Opening Polymerization ◽  
Acyl Transfer ◽  
Frontier Molecular Orbital ◽  
Functional Theory ◽  
Elimination Pathway

The thiourea-catalyzed methanolysis of d-lactide, a model system for the initiation and propagation of the organocatalyzed ring-opening polymerization (ROP) of lactide, has been studied by performing density functional theory calculations. Both the catalyzed and uncatalyzed reactions are explored along two possible pathways: one involves the stepwise addition–elimination pathway and the other is related to the concerted pathway. It is found that the reaction without the presence of the catalyst is difficult because the barrier involved is as high as 176 kJ mol–1. With the aid of a thiourea catalyst, the barrier is reduced to 88 kJ mol–1 with a preference for the stepwise addition–elimination mechanism over the concerted one. The role of the catalyst has been rationalized by analyzing the frontier molecular orbital interactions between the catalyst and substrates and by performing natural population analysis. Finally, another mechanism involving acyl transfer is discussed for the thiourea-catalyzed ROP.

Transfer of arachidonic acid from phosphatidylcholine to phosphatidylethanolamine during storage of human platelets for 5 days

1990 ◽  
Vol 68 (1) ◽  
pp. 117-122 ◽  
Author(s):  
Julie Lacasse ◽  
Rosalind S. Labow ◽  
Morris Kates ◽  
George A. Adams
Keyword(s):  
Arachidonic Acid ◽  
Storage Conditions ◽  
Phospholipid Metabolism ◽  
Human Platelets ◽  
Acyl Transfer ◽  
Acid Uptake ◽  
Molar Composition ◽  
Platelet Storage ◽  
Head Groups ◽  
Glycerol Uptake

Human platelets are routinely stored for 5 days prior to transfusion, but they deteriorate during storage. Since very little information is available concerning the effect of storage on platelet phospholipid metabolism, the biosynthesis and remodelling of platelet phospholipids were studied. Platelets were incubated separately with [14C]glycerol, [14C]arachidonic acid, or a mixture of [14C]glycerol and [3H]arachidonic acid, and stored in a platelet storage medium at 22 °C. Maximum glycerol uptake (20%) was attained after 6 h. [14C]Glycerol was incorporated into phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol, and to a much lesser extent phosphatidylserine, under storage conditions for 5 days. The distribution of the initial arachidonic acid uptake was not as would be expected based on the molar composition of endogenous phospholipids. The arachidonic acid (75%) which was taken up within 10 min of incubation distributed 55% into the phosphatidylcholine and only 14% into the phosphatidylethanolamine; the molar composition is actually 18% phosphatidylcholine and 47% phosphatidylethanolamine. During storage, there was a continuous transfer of the radiolabeled arachidonic acid from phosphatidylcholine to phosphatidylethanolamine until, after 5 days, the distribution of arachidonic acid was identical to the endogenous distribution. In contrast, no change in the glycerol incorporation pattern was detected during storage. This suggested that the mechanism for arachidonic acid redistribution was not through exchange of polar head groups, but through acyl transfer of arachidonic acid from phosphatidylcholine to phosphatidylethanolamine.Key words: human, platelet, storage, arachidonate, phospholipids.

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