Lipase-Catalyzed Oligomerization and Hydrolysis of Alkyl Lactates: Direct Evidence in the Catalysis Mechanism That Enantioselection Is Governed by a Deacylation Step

2010 ◽  
Vol 11 (8) ◽  
pp. 2008-2015 ◽  
Author(s):  
Hitomi Ohara ◽  
Akihisa Onogi ◽  
Masafumi Yamamoto ◽  
Shiro Kobayashi
Keyword(s):  
Direct Evidence ◽  
Catalysis Mechanism ◽  
Hydrolysis Of

Bidirectional RNA helicase activity of eucaryotic translation initiation factors 4A and 4F

1990 ◽  
Vol 10 (3) ◽  
pp. 1134-1144 ◽  
Author(s):  
F Rozen ◽  
I Edery ◽  
K Meerovitch ◽  
T E Dever ◽  
W C Merrick ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Translation Initiation ◽  
Direct Evidence ◽  
Rna Helicase ◽  
Initiation Factor ◽  
Helicase Activity ◽  
Ribosome Binding ◽  
Initiation Factors ◽  
Translation Initiation Factors ◽  
Hydrolysis Of

The mechanism of ribosome binding to eucaryotic mRNAs is not well understood, but it requires the participation of eucaryotic initiation factors eIF-4A, eIF-4B, and eIF-4F and the hydrolysis of ATP. Evidence has accumulated in support of a model in which these initiation factors function to unwind the 5'-proximal secondary structure in mRNA to facilitate ribosome binding. To obtain direct evidence for initiation factor-mediated RNA unwinding, we developed a simple assay to determine RNA helicase activity, and we show that eIF-4A or eIF-4F, in combination with eIF-4B, exhibits helicase activity. A striking and unprecedented feature of this activity is that it functions in a bidirectional manner. Thus, unwinding can occur either in the 5'-to-3' or 3'-to-5' direction. Unwinding in the 5'-to-3' direction by eIF-4F (the cap-binding protein complex), in conjunction with eIF-4B, was stimulated by the presence of the RNA 5' cap structure, whereas unwinding in the 3'-to-5' direction was completely cap independent. These results are discussed with respect to cap-dependent versus cap-independent mechanisms of ribosome binding to eucaryotic mRNAs.

Theoretical Evaluation of the Substrate-Assisted Catalysis Mechanism for the Hydrolysis of Phosphate Monoester Dianions

2007 ◽  
Vol 13 (13) ◽  
pp. 3617-3629 ◽  
Author(s):  
Nathalie Iché-Tarrat ◽  
Manuel Ruiz-Lopez ◽  
Jean-Claude Barthelat ◽  
Alain Vigroux
Keyword(s):  
Theoretical Evaluation ◽  
Catalysis Mechanism ◽  
Hydrolysis Of

METABOLISM OF ORGANOPHOSPHORUS INSECTICIDES: III. FATE OF THE METHYL GROUPS OF DIPTEREX IN VIVO

1965 ◽  
Vol 43 (8) ◽  
pp. 1271-1275 ◽  
Author(s):  
A. Hassan ◽  
S. M. A. D. Zayed
Keyword(s):  
Methyl Ester ◽  
Direct Evidence ◽  
Single Injection ◽  
Methyl Groups ◽  
Organophosphorus Insecticides ◽  
Ester Linkage ◽  
Hydrolysis Of ◽  
Expired Air

Direct evidence for the hydrolysis of O-methyl ester linkage(s) of Dipterex in the rat has been obtained using Dipterex in which the two methyl groups are C14-labelled. Following a single injection (i.p.) of radio-Dipterex, about 60% of the C14activity was recovered, after 24 hours, in the expired air and in the urine. C14O2and C14-formate constituted about 50% of the recovered radioactivity. The contribution of P—OCH3cleavage to the detoxification of the insecticide has been discussed. A scheme for the fate of the methyl groups has been suggested.

Choline conjugates of auxins. I. Direct evidence for the hydrolysis of choline-auxin conjugates by pea cholinesterase

2000 ◽  
Vol 38 (4) ◽  
pp. 301-308 ◽  
Author(s):  
Richard A. Fluck ◽  
Phyllis A. Leber ◽  
John D. Lieser ◽  
Sandra K. Szczerbicki ◽  
Jeffrey G. Varnes ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Auxin Conjugates ◽  
Hydrolysis Of

scholarly journals Bidirectional RNA helicase activity of eucaryotic translation initiation factors 4A and 4F.

1990 ◽  
Vol 10 (3) ◽  
pp. 1134-1144 ◽  
Author(s):  
F Rozen ◽  
I Edery ◽  
K Meerovitch ◽  
T E Dever ◽  
W C Merrick ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Translation Initiation ◽  
Direct Evidence ◽  
Rna Helicase ◽  
Initiation Factor ◽  
Helicase Activity ◽  
Ribosome Binding ◽  
Initiation Factors ◽  
Translation Initiation Factors ◽  
Hydrolysis Of

The mechanism of ribosome binding to eucaryotic mRNAs is not well understood, but it requires the participation of eucaryotic initiation factors eIF-4A, eIF-4B, and eIF-4F and the hydrolysis of ATP. Evidence has accumulated in support of a model in which these initiation factors function to unwind the 5'-proximal secondary structure in mRNA to facilitate ribosome binding. To obtain direct evidence for initiation factor-mediated RNA unwinding, we developed a simple assay to determine RNA helicase activity, and we show that eIF-4A or eIF-4F, in combination with eIF-4B, exhibits helicase activity. A striking and unprecedented feature of this activity is that it functions in a bidirectional manner. Thus, unwinding can occur either in the 5'-to-3' or 3'-to-5' direction. Unwinding in the 5'-to-3' direction by eIF-4F (the cap-binding protein complex), in conjunction with eIF-4B, was stimulated by the presence of the RNA 5' cap structure, whereas unwinding in the 3'-to-5' direction was completely cap independent. These results are discussed with respect to cap-dependent versus cap-independent mechanisms of ribosome binding to eucaryotic mRNAs.

THE STRUCTURE OF A SYNTHETIC GLUCAN: I. GENERAL STRUCTURAL FEATURES

1962 ◽  
Vol 40 (6) ◽  
pp. 1196-1200 ◽  
Author(s):  
G. G. S. Dutton ◽  
A. M. Unrau
Keyword(s):  
Petroleum Ether ◽  
Acid Hydrolysis ◽  
Direct Evidence ◽  
Periodate Oxidation ◽  
Structural Features ◽  
Degree Of Polymerization ◽  
Molar Ratio ◽  
Partial Hydrolysis ◽  
Large Numbers ◽  
Hydrolysis Of

Only D-glucose was obtained on acid hydrolysis of the glucan. Periodate oxidation released formaldehyde, which was believed to arise from C6 of D-glucofuranose units. From the additional formaldehyde liberated from the borohydride-reduced glucan the degree of polymerization was estimated to be about 165. Complete hydrolysis of the derived polyalcohol gave glycerol, erythritol, D-glucose, and D-xylose. Partial hydrolysis gave glycerol, erythritol, and at least seven non-reducing oligosaccharides. Direct evidence for the existence of relatively large numbers of 1 → 6 and 1 → 4 linkages was found, together with smaller numbers of 1 → 2 linkages. The methylated glucan was freely soluble in chloroform – petroleum ether (5:95), and hydrolysis gave tetra, tri, di, and mono-O-methyl-D-glucoses in a 6:6:3:1 molar ratio.

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