The conformational changes in aspartate transcarbamylase upon binding of substrates or regulatory ligands and the effects of alterations in the subunit structure on the allosteric interactions are reviewed. The available information including recent results from studies of the c3r6 complex (c denotes the catalytic polypeptide and r, the regulatory polypeptide) is considered in terms of the exis...

The conformational changes in aspartate transcarbamylase upon binding of substrates or regulatory ligands and the effects of alterations in the subunit structure on the allosteric interactions are reviewed. The available information including recent results from studies of the c3r6 complex (c denotes the catalytic polypeptide and r, the regulatory polypeptide) is considered in terms of the exis...

Cytochrome P450 3A4 is generally considered to be the most important human drug-metabolizing enzyme and is known to catalyze the oxidation of a number of substrates in a cooperative manner. An allosteric mechanism is usually invoked to explain the cooperativity. Based on a structure-activity study from another laboratory using various effector-substrate combinations and on our own studies using...

We develop a framework for optimizing a novel approach to extending the linear range of bioanalytical systems and biosensors by utilizing two enzymes with different kinetic responses to the input chemical as their substrate. Data for the flow injection amperometric system devised for detection of lysine based on the function of L-lysine-alpha-oxidase and lysine-2-monooxygenase are analyzed. Lys...

Lactobacillus casei allosteric L-lactate dehydrogenase (L-LDH) absolutely requires fructose 1,6-bisphosphate [Fru(1,6)P2] for its catalytic activity under neutral conditions, but exhibits marked catalytic activity in the absence of Fru(1,6)P(2) under acidic conditions through the homotropic activation effect of substrate pyruvate. In this enzyme, a single amino acid replacement, i.e. that of Hi...

Succinate Dehydrogenase-dependent Nutritional Requirement for Succinate in Mutants of Escherichia coli ~ 1 2 . By I. T. CREAGHAN and J. R. GUEST Heterothallic Phytophthora : Evidence for Hormonal Regulation of Sexual Reproduction. By W. H. KO Purification and Properties of an NAD(P)+-linked Formaldehyde Dehydrogenase from Methylococcus capsulatus (Bath). By D. I. STIRLING and H. DALTON . A Spec...