Showing papers by "Takaharu Sakiyama published in 2000"
TL;DR: The role and significance of a complex formation for the cysteine synthetase is discussed and changes in the stability of the wild-type SAT by the complex formation are discussed.
Abstract: Some properties and kinetics of the free and bound serine acetyltransferases (SATs) and O-acetylserine sulfhydrylase-As (OASS-As) from Escherichia coli were investigated. In some cases, SATΔC20, deleting 20 amino acid residues from the C-terminus of the wild-type SAT (Biosci. Biotechnol. Biochem., 63, 168-179 (1999)) was tested for comparison. The optimum pH and stability against some reagents for the free and bound wild-type SATs were similar except for the resistance to cold inactivation. The kinetics for the wild-type SAT and SATΔC20 followed a Ping-Pong Bi Bi mechanism with a mixed-type inhibition by L-cysteine. The kinetics and kinetic constants for the wild-type SAT were not changed by the complex formation with OASS-A. The optimum pH for OASS-A was shifted towards an alkaline pH by the complex formation. Thermal stability and stability against some reagents for the free and bound OASS-As were almost the same. On the other hand, the maximum velocity for OASS-A was lowered and dissociation constants ...
70 citations
TL;DR: It was indicated that 10 amino acid residues or fewer from the C-terminus of the wild-type SAT are responsible for the complex formation with OASS-A.
Abstract: Some properties of serine acetyltransferases (SATs) from Escherichia coli, deleting 10-25 amino acid residues from the C-terminus (SATdeltaC10-deltaC25) were investigated. The specific activity depended only slightly on the length of the C-terminal region deleted. Although the sensitivity of SATdeltaC10 to inhibition by L-cysteine was similar to that for the wild-type SAT, it became less with further increases in the length of the amino acid residues deleted. SATdeltaC10 was inactivated on cooling to 0 degrees C and dissociated into dimers or trimers in the same manner as the wild-type SAT, but Met-256-le mutant SAT as well as SATdeltaC14, SATdeltaC20, and SATdeltaC25 were stable. Since SATdeltaC10, SATdeltaC14, and SATdeltaC25 did not form a complex with O-acetylserine sulfhydrylase-A (OASS-A) in a way similar to SATdeltaC20, it was indicated that 10 amino acid residues or fewer from the C-terminus of the wild-type SAT are responsible for the complex formation with OASS-A. The C-terminal peptide of the 10 amino acid residues interacted competitively with OASS-A with respect to OAS although its affinity was much lower than that for the wild-type SAT.
55 citations
TL;DR: An experimental realization of a gel system in which frustrations exist and can be minimized, thus meeting two crucial criteria predicted to enable memory of conformations in polymers.
Abstract: We report an experimental realization of a gel system in which frustrations exist and can be minimized, thus meeting two crucial criteria predicted to enable memory of conformations in polymers. The gels consist of a thermosensitive major monomer component and two minor components. One minor component is positively charged and will form complexes around negatively charged target molecules placed in solution. The complexes can be imprinted into the gel by then cross-linking the second minor component, which will form cross-links additional to those in the major polymer matrix. The complexes are destroyed and reformed upon swelling and reshrinking of the gels, showing that memorization has been achieved.
53 citations
TL;DR: Investigating the adsorption behavior of various amino acids on a stainless steel surface suggested that the acidic and basic amino acids adsorb through two electrostatic interactions of two ionized groups in the amino acid with a Stainless steel surface.
44 citations
TL;DR: The initial kinetics for the syntheses of N-(benzyloxycarbonyl)-L-alanyl-L-phenylalanine methyl ester and ZDPM in an aqueous/organic biphasic system, using free thermolysin were elucidated, both experimentally and theoretically.
9 citations
TL;DR: In this article, a novel advanced oxidation system using a combined UV/H2O2 technique was constructed for application to wastewater treatment, which takes into account the formation as well as the disappearance rate of hydroxyl radical (•OH), distribution of UV illuminance along the depth of the flow, and the rate of reaction between dye and •OH, to simulate the course of dye decomposition.
Abstract: A novel advanced oxidation system using a combined UV/H2O2 technique was constructed for application to wastewater treatment. In this system, wastewater containing H2O2 flows along a channel with a flat surface in a thin film, onto which surface UV rays with a wavelength of 253.7 nm are irradiated. As a model wastewater, we used various dye solutions and investigated decoloration rates under various conditions differing in H2O2 concentration, temperature, UV illuminance, and so on. Based on the model, which takes into consideration the formation as well as the disappearance rate of hydroxyl radical (•OH), distribution of UV illuminance along the depth of the flow, and the rate of reaction between dye and •OH, we could simulate the course of dye decomposition. Furthermore, we showed the existence of an optimum H2O2 concentration for decomposition on the basis of this model.
5 citations
TL;DR: N-(Benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester, a precursor of the synthetic sweetener aspartame, was synthesized, using thermolysin immobilized onto Amberlite XAD-7, both in ethyl acetate and in tert-amyl alcohol.
1 citations