Glycogen phosphorylase a and b are irreversibly inactivated by oxidation with the disulfide cystamine. The mechanism is complex and involves oxidation of at least two classes of sulfhydryl groups. The oxidation of one or more of the first class of 4 f 1 sulfhydryl groups is reversible, but the equilibrium constant for the oxidation is so unfavorable (1 X that the micromolar concentrations of cy...

1. The rate of inactivation of crystalline trypsin solutions and the nature of the products formed during the inactivation at various pH at temperatures below 37 degrees C. have been studied. 2. The inactivation may be reversible or irreversible. Reversible inactivation is accompanied by the formation of reversibly denatured protein. This denatured protein exists in equilibrium with the native ...

Neisseria gonorrhoeae dihydrofolate reductase undergoes a time-dependent, irreversible inactivation by 2,4-diamino-5-[3,5-dimethoxy-4-(p-bromoacetamidophenoxy)benzyl] pyrimidine. The kinetics of inactivation are consistent with the reversible formation of an enzyme-inhibitor complex followed by covalent binding to the enzyme. The reversible component is competitive with dihydrofolate and has an...

1. c-Mannosidase from jack-bean meal was pturified 150-fold. fl-N-Acetylglucosaminidase and f-galactosidase were removed from the preparation by treatment with pyridine. Zn2+ was added during the purification to stabilize the cxmannosidase. 2. At pH values below neutrality, x-mannosidase undergoes reversible spontaneous inactivation at a rate dependent on the temperature, the degree of dilution...

Effect of concentrated urea on JE virus was studied with a special view upon the structure of the virion. Urea concentration less than 2M acted reversibly to destroy the particles at 24 C in a wide range of pH between 7.2 and 10.0. At concentrations of urea higher than 3 M up to 8 M, the particles were disrupted irreversibly with a rapid loss of both infectivity and hemagglutinating activity. A...

Drug-drug interactions (DDIs) that occur via mechanism-based inactivation of cytochrome P450 are of serious concern. Although several predictive models have been published, early risk assessment of MBIs is still challenging. For reversible inhibitors, the DDI risk categorization using [I]/K(i) ([I], the inhibitor concentration; K(i), the inhibition constant) is widely used in drug discovery and...

Drug-drug interactions (DDIs) that occur via mechanism-based inactivation of cytochrome P450 are of serious concern. Although several predictive models have been published, early risk assessment of MBIs is still challenging. For reversible inhibitors, the DDI risk categorization using [I]/Ki ([I], the inhibitor concentration; Ki, the inhibition constant) is widely used in drug discovery and dev...

Introduction: The role of serotonergic fibers in avoidance learning is controversial. Involvement of the dorsal raphe nucleus (DRN), the main source of hippocampal projecting serotonergic fibers in acquisition, consolidation and retrieval of passive avoidance (PA) learning, was investigated by functional suppression of this area. Materials and Methods: DRN functional inactivation was done by li...

Introduction: Several supra spinal areas such as rostral ventrolateral medulla (RVLM) area are involved in basic cardiovascular regulation. The Kolliker— Fuse nucleus (KF) is located in pons and is heavily connected with RVLM. The cardiovascular effect of KF nucleus has been shown and it is suggested that KF is involved in sympathetic vasomotor tone and basic cardiovascular regulation. Therefor...

Treatment of 3-aminopyridine adenine dinucleotide phosphate with sodium periodate resulted in oxidation of the ribose linked to 3-aminopyridine ring and cleavage of the dinucleotide into 3-aminopyridine and adenosine moieties. These two moieties were separated by thin layer chromatography and were synergistically bound to pigeon liver malic enzyme (EC 1.1.1.40), causing inactivation of the enzy...