The RecA and some related proteins possess a simple motif, called (KR)X(KR), that (in RecA) consists of two lysine residues at positions 248 and 250 at the subunit-subunit interface. This study and previous work implicate this RecA motif in the following: (a) catalyzing ATP hydrolysis in trans,(b) coordinating the ATP hydrolytic cycles of adjacent subunits, (c) governing the rate of ATP hydroly...

Acid-catalyzed hydrolysis of the methox-ytropone moiety of colchicine has been shown to proceed at a greater rate than in the case of isocolchicine1. (Struc­ tures are shown in Table I.) No interpretation of this rate difference has been offered. And, while a mecha­ nism for the acid-catalyzed hydrolysis of 2 -methoxytropone has been proposed2, no kinetic data on this type of reaction either fo...

Neutrase 0.8L and N120P proteases were used for oligopeptide production from apricot almonds meal, and response surface design was carried out to optimize the effect of hydrolysis conditions on hydrolysis degree (DH) and oligopeptide yield rate. Four independent variables were used to optimize the hydrolysis process: hydrolysis temperature (X(1)), enzyme-to substrate ratio (E/S) (X(2)), substra...

Considerable uncertainty surrounds the stoichiometry of coupling of ATP hydrolysis to drug pumping by P-glycoprotein, the multidrug transporter. To estimate relative turnovers for pumping of the drug vinblastine and ATP hydrolysis, we began by measuring the number of P-glycoprotein molecules on the surface of murine NIH3T3 cells expressing the human MDR1 gene. Fluorescence of cells treated with...

Contrary to the report of Bergmann and Fruton (1) the L peptide present in aqueous solutions of N-benzoyl-DL-tyrosylglycinamide, prepared by two independent methods, is rapidly hydrolyzed by crystalline chymotrypsin. At 40” and pH 7.8 in a 0.00344 M solution’ of the DL mixture the L component is hydrolyzed as rapidly as in a 0.00172 M solution of the L peptide (Table I). Because of the relative...

In this work, the interconversion of GHB and GBL in a variety of aqueous media was studied. The effects of solution pH and time were determined by spiking GHB or GBL into pure water and buffered aqueous solutions, and determining the GHB and GBL contents at various time intervals. The degree of GBL hydrolysis to GHB was determined for several commercial aqueous-based GBL products, and further s...

The kinetics of binding and hydrolysis of ATP by bovine cardiac myosin subfragment 1 has been reinvestigated. More than 90% of the total fluorescence amplitude associated with ATP hydrolysis occurs with an apparent second-order rate constant of 8.1 X 10(5) M-1 S-1 and a limiting rate constant of approximately 140 S-1 (100 mM KCl, 50 mM 1,3-bis-[tris(hydroxymethyl)methylamino]-propane, 10 mM MgC...

The difference in relative rates of hydrolysis of the 1,3and the 2-ester bonds of triglycerides (50-100: 1) catalyzed by pancreatic lipase results in a rapid net hydrolysis of the 1,3-ester bonds at an enzyme level that effects only limited hydrolysis of the 2-ester bond. The net hydrolysis of the 1,3or primary ester bonds proceeds until a steady state has been established between rate of hydro...

The kinetics of ATP hydrolysis and tension responses were studied simultaneously in a permeabilized preparation of cardiac tissue of the guinea pig. This was achieved by combining laserflash photolysis of P3-1-(2-nitrophenyl)ethyladenosine 5'-triphosphate ("caged-ATP") and a rapid freezing technique. In the presence of calcium ions, tension increased following the photolytic production of ATP w...

Urea kinetics were measured using prime/intermittent oral doses of [15N15N]urea, on five separate protocols in thirteen normal young women. Each woman underwent either two or three study protocols. Measurements were made at day 12 and day 22 of the menstrual cycle, whilst consuming their habitual protein intake in seven women not taking the contraceptive pill and in six women taking the contrac...