pH and kinetic isotope effects on the oxidative half-reaction of D-amino-acid oxidase.

D-Amino-acid oxidase catalyzes the oxidation of D-amino acids to imino acids. In the oxidative half-reaction, oxygen reacts with the reduced enzyme-imino acid complex to reoxidize the bound FAD. This is then followed by dissociation of the imino acid.

Bifunctional peptidylglcine alpha-amidating enzyme requires two copper atoms for maximum activity.

The conversion of C-terminal glycine-extended peptides to C-terminal alpha-amidated peptides occurs in two distinct reactions, both of which are catalyzed by bifunctional peptidylglycine alpha-amidating enzyme. The first step is the alpha-hydroxylation of the C-terminal glycine residue and the second step is the dealkylation of the alpha-hydroxyglycine-extended peptide to the alpha-amidated peptide and glyoxylate. We show that the bifunctional enzyme requires 1.

Eigenvalues of the inertia tensor and exteroception by the "muscular sense".

Muscle spindles and Golgi tendon organs constitute the receptor foundation to the "muscle sense." Muscle sensitivity has long been assumed relevant to the non-visual perception of the positions and motions of the body's segments and of the properties of hand-held objects. Dynamic touch is the label given to the particular kind of tactile exteroperception that involves a non-spatial input from muscles and tendons.

Clinical and cognitive effects of methylphenidate on children with attention deficit disorder as a function of aggression/oppositionality and age.

Children diagnosed with attention deficit disorder (ADD; n = 44), ADD plus aggression/oppositionality (ADD/O; n = 34), and as not meeting ADD criteria (NC; n = 29) received methylphenidate and placebo for 21 consecutive days each. Parents and teachers rated all groups improved under medication, but teachers reported less improvement for NC than for ADD/O children. Methylphenidate and chronological age had generally similar effects in a Sternberg task: greater accuracy and speed (especially for nontargets at low memory loads), larger P3b waves of event-related potentials, more pronounced slowing of P3b latency by memory load, and a greater trend of earlier peaks for targets than for nontargets.

Nitrofurantoin: mechanism of action and implications for resistance development in common uropathogens.

Nitrofurantoin is an effective urinary tract antibacterial to which no clinically significant resistance development has occurred. We have previously shown that nitrofurantoin susceptibility in bacteria correlates with the presence of bacterial nitroreductases which convert nitrofurantoin to highly reactive electrophilic intermediates. These intermediates were shown to attack bacterial ribosomal proteins non-specifically, causing complete inhibition of protein synthesis.

Intrinsic primary, secondary, and solvent kinetic isotope effects on the reductive half-reaction of D-amino acid oxidase: evidence against a concerted mechanism.

D-Amino acid oxidase catalyzes the oxidation of D-amino acids to imino acids with subsequent transfer of the electrons to molecular oxygen. Proposed mechanisms for the mode of cleavage of the substrate CH bond include stepwise formation of a carbanion, followed by attack of the carbanion on the enzyme-bound FAD, direct hydride transfer of the substrate alpha-hydrogen to the FAD, and transfer of a hydride from the substrate amino group to the FAD. Conditions have previously been established under which large, limiting, primary deuterium kinetic isotope effects can be measured with D-alanine, D-serine, and glycine as substrates for D-amino acid oxidase [Denu, J.

X-ray crystal structure of cross-linked subtilisin Carlsberg in water vs. acetonitrile.

The crystal structure of subtilisin Carlsberg lightly cross-linked with glutaraldehyde was solved in aqueous solution by X-ray crystallography at 2.3 A resolution. It was found to be virtually identical to the recently determined (Fitzpatrick, P.

Identification of the intersubunit binding region in rat tyrosine hydroxylase.

Limited proteolysis converts the 39200 molecular weight catalytic domain of rat tyrosine hydroxylase to a monomer with a molecular weight of 37600. The purified monomer is almost fully active, with minor changes in kinetic parameters at pH 7. Mass spectral analysis and N-terminal sequencing of the proteolytically generated species establish that 20 amino acids have been removed from the carboxyl terminus and five from the amino terminus.

3D image reconstruction of right subclavian artery aneurysms.

Objective: Three-dimensional (3D) image reconstruction methods allied to spiral CT (SCT) or MR angiography (MRA) are used in clarifying the anatomy of complex aortic anatomy.

Materials And Methods: Two patients with superior mediastinal masses suggestive of aneurysms of the anomalous right subclavian artery were examined. Both patients were examined using breath-hold SCT and one by breath-hold MRA.

Enzyme crystal structure in a neat organic solvent.

The crystal structure of the serine protease subtilisin Carlsberg in anhydrous acetonitrile was determined at 2.3 A resolution. It was found to be essentially identical to the three-dimensional structure of the enzyme in water; the differences observed were smaller than those between two independently determined structures in aqueous solution.

Expression and characterization of catalytic and regulatory domains of rat tyrosine hydroxylase.

Phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase constitute a family of tetrahydropterin-dependent aromatic amino acid hydroxylases. Comparison of the amino acid sequences of these three proteins shows that the C-terminal two-thirds are homologous, while the N-terminal thirds are not. This is consistent with a model in which the C-terminal two-thirds constitute a conserved catalytic domain to which has been appended discrete regulatory domains.

Commentary: development of perception-action systems and general principles of pattern formation.

Our commentary on this special issue devoted to Developmental Biodynamics: Brain, Body, and Behavior Connections is divided into 3 main sections. The first section is an overview of the individual contributions. 5 major themes are identified: (1) inappropriateness of computational treatments of development and the need for more biologically and physically relevant treatments; (2) significance of tailoring muscular to nonmuscular forces in developing movement coordination; (3) importance of spontaneous movements as exploratory and formative mechanisms; (4) influences of action capabilities on the development of perception capabilities, and vice versa; (5) applications of methods and techniques of nonlinear dynamics to developmental processes.

Separation of multiple forms of glutathione S-transferase from the blue mussel, Mytilus edulis.

1. Glutathione S-transferase isoenzymes from Mytilus edulis and M. galloprovincialis have been partially purified by glutathione-sepharose affinity chromatography followed by Mono Q anion exchange fast protein liquid chromatography (f.

Tensorial basis to the constancy of perceived object extent over variations of dynamic touch.

Subjects wielded occluded rods, with or without attached masses, and reported the distances reachable with their distal tips. Experiments 1-3 compared wielding about the wrist, the elbow, and the shoulder. Experiments 4 and 5 compared free wielding, using the whole arm, with wielding only about the wrist.

Lysine241 of tyrosine hydroxylase is not required for binding of tetrahydrobiopterin substrate.

The lysine residues at positions 194 and 198 in phenylalanine hydroxylase have been shown to react with a photoaffinity label which is an analog of phenyltetrahydropterin (Gibbs, B. S., and Benkovic, S.

Intravenous thrombolytic therapy in myocardial infarction: an analytical review.

The properties and physiological effects of three currently FDA-approved thrombolytic agents, streptokinase (SK), tissue plasminogen activator (tPA), and anisoylated plasminogen activator complex (APSAC) are reviewed. All thrombolytic agents have been shown to reduce mortality postmyocardial infarction (MI). Comparative trials have failed to demonstrate a difference between the effects of tPA, SK, and APSAC on mortality.

pH and kinetic isotope effects on the reductive half-reaction of D-amino acid oxidase.

Primary deuterium kinetic isotope and pH effects on the reduction of D-amino acid oxidase by amino acid substrates were determined using steady-state and rapid reaction methods. With D-serine as substrate, reduction of the enzyme-bound FAD requires that a group with a pKa value of 8.7 be unprotonated and that a group with a pKa value of 10.

Computer-assisted modeling of subtilisin enantioselectivity in organic solvents.

In order to rationalize our discovery of a marked dependence of subtilisin's enantioselectivity on the organic solvent used as the reaction medium, we employed the X-ray crystal structure of the enzyme and the means of interactive computer modeling to construct the structures of the reactive enzyme-substrate complexes. For subtilisin-catalyzed trans-esterifications between vinyl butyrate and S and R enantiomers of chiral secondary alcohols XCH(OH)Y, the computer simulation data clearly explain a higher reactivity of the former enantiomer on the basis of severe steric hindrances experienced by the latter enantiomer in the active site of subtilisin. The models of binding derived by computer modeling also successfully predicted changes in subtilisin enantioselectivity as a function of the sizes of the X and Y substituents in the nucleophile and upon addition of certain inhibitors.

The amino acid substrate of bovine tyrosine hydroxylase.

Tyrosine hydroxylase catalyzes the tetrahydropterin-dependent hydroxylation of tyrosine to form 3,4-dihydroxyphenylalanine. Several nonphysiological aromatic amino acids have been examined as inhibitors and substrates for bovine adrenal tyrosine hydroxylase. The Ki values for para-substituted phenylalanines increase as the size of the substituent increases.

An animal model of fibrinolytic bleeding based on the rebleed phenomenon: application to a study of vulnerability of hemostatic plugs of different age.

The primary bleeding time is prolonged when tested during the infusion of both plasminogen activators and anticoagulants, and such sites frequently exhibit rebleeding after initial hemostatic control. This study describes an animal (rabbit) model which distinguishes fibrinolytic from anticoagulant hemorrhage and further applies the model to the study of hemostatic plugs of increasing age. In this model, rebleeding occurred from hemostatically-stable ear puncture sites induced prior to infusion of streptokinase (SK) or recombinant tissue-plasminogen activator (rt-PA), but not of heparin or hirudin.

Site-directed mutagenesis of serine 40 of rat tyrosine hydroxylase. Effects of dopamine and cAMP-dependent phosphorylation on enzyme activity.

Rat tyrosine hydroxylase expressed with a baculovirus expression system contains covalent phosphate and has kinetic parameters consistent with those expected of phosphorylated enzyme (Fitzpatrick, P. F., Chlumsky, L.

Haptic probing: perceiving the length of a probe and the distance of a surface probed.

Knowing about the properties of objects by wielding them and knowing about the distances of surfaces by striking them with objects as probes are examples of dynamic or effortful touch. Six experiments focused on the invariant mechanical parameters that couple the time-varying states (displacements, velocities) of hand-held rods to the time-varying torques and forces imposed upon them by wielding and probing. There were three major conclusions.