Cleavage of amyloid precursor protein (APP) by the beta- and gamma-secretases generates the amino and carboxy termini, respectively, of the A beta amyloidogenic peptides A beta40 and A beta42--the major constituents of the amyloid plaques in the brain parenchyma of Alzheimer's disease patients. There is evidence that the polytopic membrane-spanning proteins, presenilin 1 and 2 (PS1 and PS2), are important determinants of gamma-secretase activity: mutations in PS1 and PS2 that are associated with early-onset familial Alzheimer's disease increase the production of A beta42 (refs 4-6), the more amyloidogenic peptide; gamma-secretase activity is reduced in neuronal cultures derived from PS1-deficient mouse embryos; and directed mutagenesis of two conserved aspartates in transmembrane segments of PS1 inactivates the ability of gamma-secretase to catalyse processing of APP within its transmembrane domain. It is unknown, however, whether PS1 (which has little or no homology to any known aspartyl protease) is itself a transmembrane aspartyl protease or a gamma-secretase cofactor, or helps to colocalize gamma-secretase and APP. Here we report photoaffinity labelling of PS1 (and PS2) by potent gamma-secretase inhibitors that were designed to function as transition state analogue inhibitors directed to the active site of an aspartyl protease. This observation indicates that PS1 (and PS2) may contain the active site of gamma-secretase. Interestingly, the intact, single-chain form of wild-type PS1 is not labelled by an active-site-directed photoaffinity probe, suggesting that intact wild-type PS1 may be an aspartyl protease zymogen.

Thymine hydroxylase from Rhodotorula glutinis catalyzes the oxidation of thymine to its alcohol, aldehyde, and carboxylic acid in three successive reactions. Each step involves stoichiometric consumption of O2 and alpha-ketoglutarate and formation of CO2 and succinate. Given the promiscuity of this enzyme, it was hoped that it would serve as a prototype for understanding the mechanism of this class of enzymes, the non-heme Fe2+ dioxygenases. Kinetic parameters for thymine, O2, Fe2+, and alpha-ketoglutarate have been determined, and isotope effect analysis of (trideuteriomethyl)thymine with enzyme reveals D(V) = 2.08 and D(V/K) = 1.11 at saturating O2. The kinetic parameters for (hydroxymethyl)uracil oxidation have been determined, and incubation of (5'-R)- and (5'-S)-[5'-2H]-5-(hydroxymethyl)uracil with enzyme reveals stereospecific removal of the pro-S hydrogen. No apparent isotope effect is observed in this reaction. The substrate specificity of this enzyme has been examined in detail. The enzyme can catalyze epoxidation, oxidation of a thioether to a sulfoxide and a sulfone, hydroxylation of an unactivated carbon-hydrogen bond, and oxidation of a methylamine to formaldehyde, as revealed through studies with 5-vinyluracil, 5-(methylthio)uracil, 5,6-dihydrothymine, and 1-methylthymine, respectively. In each case, the products were identified by gas chromatography-mass spectrometry, and 18O2-labeling studies revealed that one atom from O2 is incorporated into each product. The enzyme has also been shown to catalyze an uncoupling of hydroxylation and decarboxylation in the presence of a substrate analog incapable of undergoing hydroxylation or a substrate that is difficult to oxidize.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract

No abstract

A high-throughput screen at 100 microM inhibitor concentration for the BACE-1 enzyme revealed a novel spiropiperidine iminohydantoin aspartyl protease inhibitor template. An X-ray cocrystal structure with BACE-1 revealed a novel mode of binding whereby the inhibitor interacts with the catalytic aspartates via bridging water molecules. Using the crystal structure as a guide, potent compounds with good brain penetration were designed.

No abstract

No abstract

An unprecedented catalytic asymmetric synthesis of aminal‐containing heterocyclic compounds has been developed from imines and tethered nitrogen/nitrogen nucleophiles. In the presence of 10 mol% of a commercially available chiral phosphoric acid, a range of aromatic, α,β‐unsaturated, and aliphatic imines react with 2‐aminobenzamides to give dihydroquinazolinones in good to excellent yields and ee. The enantioselectivity is significantly affected by the imine N‐substituent through non‐bonding interactions with the chiral phosphoric acid and the 2‐aminobenzamide.