The purpose of this study is to investigate if a readily available cell line (APRE-19) may be used to study in vitro function of visual cycle enzymes such as lecithin:retinol acyltransferase (LRAT). Cells incubated with exogenous retinol accumulated intracellular all-trans retinol and all-trans retinyl ester. Membrane proteins from ARPE-19 exhibited LRAT activity, which was inhibited by an LRAT...

Two or possibly three equivalents of N-bromoacetylacetazolamide interact with two histidine residues located in the active site region of human carbonic anhydrase B. The most rapid reaction occurs at the l-nitrogen of a histidine residue and this is followed by a slower alkylation of the 3-nitrogen of the same histidine and the 3-nitrogen of a second histidine. From a reaction mixture of N-brom...

The conformation of the 1: 1 complex of protoporphyrin IX and apomyoglobin was studied by circular dichroism, potentiometric titration, and reaction with bromoacetate. Circular dichroism studies indicate that protoporphyrin and heme similarly affect the o-helix content of apomyoglobin. The apparent number of normal imidazoles in the protoporphyrin-apomyoglobin complex, as judged by reactivity t...

Analysis of mutations affecting the androgen receptor protein in human cells has been limited because of the low abundance and lability of these proteins in target tissues. All methods used to date have been based on the noncovalent interaction of radiolabeled androgens with the receptor's ligand binding site. We report here synthesis and use of the electrophilic affinity label dihydrotestoster...

A general procedure for the synthesis of enantiopure â-substituted, â-amino acids is presented. Alkylation of the sodium enolates derived from chiral N-acyloxazolidinone imides 2 (R ) Me, i-Pr, t-Bu, Ph, Bn) with tert-butyl bromoacetate afforded the 2-substituted succinate derivatives 3 in good yields (82-89%) and with high selectivity (g93:7). Following hydrolysis, Curtius rearrangement of the...

N a z m i A . K a s s a b , S a n a a 0 . A b d A l l a h , a n d S a i d A . E l b a h a i i Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt Z. Naturforsch. 34b, 507-510 (1979); received September 28, 1978 Arylhydrazonorhodanines, Arylhydrazonoisorhodanines, Ring Cleavage, Triazolinones, Alkylation The 5-arylhydrazono derivatives of rhodanine and isorhodanine were su...

BACKGROUND Heterobifunctional cross-linking agents are useful in both protein science and organic synthesis. Aminolysis of reactive esters in aqueous systems is often used in bioconjugation chemistry, but it must compete against hydrolysis processes. Here we study the kinetics of aminolysis and hydrolysis of 2-S-phosphorylacetate ester intermediates that result from displacement of bromide by a...

BACKGROUND Enzymatic approaches have become promising alternatives to chemical methods for the production of semi-synthetic β-lactam antibiotics. In this work, enzymatic synthesis of N-bromoacetyl-7-aminocephalosporanic acid (N-bromoacetyl-7-ACA), the key intermediate for the production of cefathiamidine, was reported for the first time. RESULTS Of the immobilized penicillin acylases (PAs) te...

Enantiopure cis-dihydrodiol bacterial metabolites of substituted benzene substrates were used as precursors, in a chemoenzymatic synthesis of the corresponding benzene oxides and of a substituted oxepine, via dihydrobenzene oxide intermediates. A rapid total racemization of the substituted benzene 2,3-oxides was found to have occurred, via their oxepine valence tautomers, in accord with predict...