Hydrolysis activity

LD model, see Langevin dipoles model (LD) Linear free-energy relationships, see Free energy relationships, linear Linear response approximation, 92,215 London, see Heitler-London model Lysine, structure of, 110 Lysozyme, (hen egg white), 153-169,154. See also Oligosaccharide hydrolysis active site of, 157-159, 167-169, 181 calibration of EVB surfaces, 162,162-166, 166... 

S. Singh, M. Scigelova, and D. H. G. Crout, Glycosidase-catalysed synthesis of mannobioses by the reverse hydrolysis activity of alpha-mannosidase Partial purification of alpha-mannosidases from almond meal, limpets and Aspergillus niger, Tetrahedron Asymmetry, 11 (2000) 223-229. 

The ester was screened against a panel of enzymes for hydrolysis activity from which only Novozym 435 efficiently hydrolysed the desired (5)-enantiomer." After significant optimization studies using Novozym 435, a process was established where a 100 g slurry of racemic ester in commercial tert-butanol (which is supplied as a mixture containing 12 % water - anhydrous terf-butanol could not be used due to its higher melting point), furnished the desired acid in 43% yield and >99% ee (Scheme 1.36). The reaction was performed at 50 °C as a compromise that gave satisfactory substrate concentration... 

This enzyme [EC 2.3.1.35], also known as ornithine ace-tyltransferase, and ornithine transacetylase, catalyzes the reversible reaction of A -acetyl-L-ornithine with L-gluta-mate to produce L-ornithine and A-acetyl-L-glutamate. This protein also exhibits a low hydrolysis activity (about 1% of that of the transferase activity) of iV -acetyl-L-ornithine to yield acetate and L-ornithine. This enzyme is not identical with A-acetylglutamate synthase [EC 2.3.1.1]. 

Due to the relative ease of oxidation of the parent compound, common delivery forms in cosmetic formulations and clinical trials are vitamin E acetate (a-TAc, structure in Fig. 15.7a) and vitamin E phosphate. These forms are expected to permeate and to regenerate free active a-TH through enzyme-catalyzed hydrolysis activities in skin. Although a-TAc is readily hydrolyzed by esterase action to vitamin E upon oral ingestion, no consensus as to the extent of bioconversion of topically applied a-TAc has been reached. Two published studies demonstrate bioconversion up to 10-15% in the viable epidermis [35] including the basal layer [36]. These and other studies show no detectable metabolism of a-TAc in stratum corneum [37]. 

Phosphodiesterase (Hydrolysis) Activity. A rather broad substrate specificity is exhibited by the purified phospholipase D (phosphodiesterase activity). It can attack phosphatidylcholine, phosphatidylethanolamine, phospha-tidylserine, and phosphatidylglycerol. In most cases, Ca2+ was an activator, but variable results were obtained on the positive influence of diethyl ether on the catalytic activity of different sources of this enzyme. Usually the optimum pH was in the range from 5.0 to 7.0. Mammalian phospholipase D, containing both the phosphodiesterase and transphosphatidylase activities, exhibited a broad-range substrate specificity similar to that of the plant enzyme. However, the mammalian enzyme showed a dependency for the presence of oleic acid in the reaction system (Kobayashi and Kanfer, 1991). 

Enzyme (older names) Specific data Mechanism of hydrolysis Activity and substrates Cinetics... 

Lysomal Glycolipid Hydrolysis, Activator Proteins for (Conzelmann and... 

Senior and colleagues have introduced a reporter tryptophan in the catalytic sites of Escherichia coli Fi (EFi) and directly measured the site occupancy. They have shown that the ATP hydrolysis activity parallels the occupancy of the third site, implicating a tri-site mechanism where the site occupancy alternates between two and three, being three during the rate-limiting step of the catalysis [31,32], Studies on TFi basically corroborated the results [33,34],... 

Our recent work using a reporter tryptophan in a mutant TF (R. Shimo-Kon et ah, unpublished) has also shown that the occupancy rises to three as [ATP] increases. The rise, however, is preceded by the rise in hydrolysis activity at the [ATP] where the activity is half maximal Km), the occupancy is only slightly above two. At Km, Fi spends half of its time at the 0° (ATP-waiting) position and the other half at 80° (Fig. 14.2). For the time-averaged occupancy to be close to two, ADP has to be released during the 80° substep or immediately (well within the 80° dwell time of 2 ms) after the 80° rotation. At [ATP] Km, the asterisked vacated site in Fig. 14.2 can bind medium nucleotide weakly, allowing the occupancy to rise to three. The study has also shown that, at least for the particular mutant studied, bi-site activity is virtually absent. 

As we truncate the y axle from the tip step by step, the bulk hydrolysis activity gradually diminishes, whereas the apparent torque becomes approximately half that of the wild type at the C-terminal truncation nearly level with the N-terminus and thereafter remains constant [42,43]. It appears that a rigid axle and bottom support are needed for high-speed catalysis and generation of full torque, but orifice interactions alone can produce half the torque. 

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