Cellular uptake of vitamin A, production of visual chromophore and triglyceride homeostasis in adipocytes depend on two representatives of the vertebrate N1pC/P60 protein family, lecithin:retinol acyltransferase (LRAT) and HRAS-like tumor suppressor 3 (HRASLS3). Both proteins function as lipid-metabolizing enzymes but differ in their substrate preferences and dominant catalytic activity. The me...

A bioinformatic and phylogenetic study has been performed on a family of penicillin-binding proteins including D-aminopeptidases, D-amino acid amidases, DD-carboxypeptidases, and β -lactamases. Significant homology between D-aminopeptidase from Ochrobactrum anthropi and other members of the family has been shown and a number of conserved residues identified as S62, K65, Y153, N155, H287, and G2...

In this study, we present the results from the semiempirical molecular orbital calculations for the acylation step in the lipase-catalyzed ester hydrolysis. The results reveal that the lowest energy path for the formation of the tetrahedral intermediate is for the serine residue of the catalytic triad to attack the substrate, followed by coupling heavy atom movement and proton transfer. The cal...

A primary-alkyl-substituted selenenyl iodide was successfully synthesized through oxidative iodination of a selenol with N-iodosuccinimide by taking advantage of a cavity-shaped steric protection group. The selenenyl iodide exhibited high thermal stability and remained unchanged upon heating at 100 °C for 3 h in [D₈]toluene. The selenenyl iodide was reduced to the corresponding selenol by treat...

Metallo-β-lactamases inactivate most β-lactam antibacterials, and much attention has been paid to their catalytic mechanism. One issue of controversy has been whether β-lactam hydrolysis generally proceeds through an anionic intermediate bound to the active-site Zn(II) ions or not. The formation of an intermediate has not been shown conclusively in imipenemase (IMP) enzymes to date. Here, we pr...

The influence of the methylphosphoester group on the reversible reaction shown below was studied. Evaluation of the rate constants for the system depicted as well as for the analogous equilibrium involving the nucleoside deoxyguanosine showed that whereas the chloride anation is slowed down by the presence of the methylphosphoester group, the hydrolysis rate constant is not significantly altere...

Experiments are reported on the uni-site catalysis and the transition from uni-site to multi-site catalysis with bovine heart mitochondrial F1-ATPase. The very slow uni-site ATP hydrolysis is shown to occur without tightly bound nucleotides present and with or without Pi in the buffer. Measurements of the transition to higher rates and the amount of bound ATP committed to hydrolysis as the ATP ...

The reuteransucrase enzymes of Lactobacillus reuteri strain 121 (GTFA) and L. reuteri strain ATCC 55730 (GTFO) convert sucrose into alpha-d-glucans (labelled reuterans) with mainly alpha-(1-->4) glucosidic linkages (50% and 70%, respectively), plus alpha-(1-->6) linkages. In the present study, we report a detailed analysis of various hybrid GTFA/O enzymes, resulting in the identification of spe...

Catalytic Properties and Mechanism Studies of the PepQ Prolidase from Escherichia coli. (August 2005) Min Sun Park., B.S., Sogang University Chair of Advisory Committee: Dr. Frank M. Raushel The PepQ prolidase from Escherichia coli catalyzes the hydrolysis of dipeptide substrates with proline residues at the C-terminus. The PepQ gene has been cloned, overexpressed and the enzyme purified to hom...

Metallo-β-lactamases are native zinc enzymes that catalyse the hydrolysis of β-lactam antibiotics, but are also able to function with cobalt(II) and require one or two metal-ions for catalytic activity. The hydrolysis of cefoxitin, cephaloridine and benzylpenicillin catalysed by CoBcII (cobalt-substituted βlactamase from Bacillus cereus) has been studied at different pHs and metal-ion concentra...