The equilibrium constants for the tryptophan binding to indoleamine 2,3-dioxygenase, a protohemoprotein, in its ferric (Fe3+), ferrous (Fez+), and CO-bound (Fea+CO) forms were determined by the spectrophotometric titration method. All these enzyme derivatives showed marked spectral changes upon tryptophan binding. Such a spectral change for the ferric enzyme was, however, specific to the L isom...

Allosteric interactions in the cupro-heme enzyme tryptophan oxygenase (EC 1.13.11.11) of Pseudomonas acidovorans are shown to be pH-dependent. Increasing the assay pH from 6.0 to 8.0 progressively desensitizes the enzyme from both homotropic and heterotropic ligand interactions. This pH-dependent reversible transition has a pK of 6.2. Hill coefficients for the substrate L-tryptophan of 2.0 and ...

It has been demonstrated, that long-term chronic tryptophan deficiency, results in decreased serotonin synthesis, which may lead to low bone mass and low bone formation. Findings from studies in male patients with idiopathic osteoporosis suggested a decreased transport of tryptophan in erythrocytes of osteoporotic patients, indicating that serotonin system defects may be involved in the etiolog...

We have investigated the pH dependence of the dynamics of conformational fluctuations of green fluorescent protein mutants EGFP (F64L/S65T) and GFP-S65T in small ensembles of molecules in solution by using fluorescence correlation spectroscopy (FCS). FCS utilizes time-resolved measurements of fluctuations in the molecular fluorescence emission for determination of the intrinsic dynamics and the...

BACE-1 is the β-secretase responsible for the initial amyloidogenesis in Alzheimer's disease, catalyzing hydrolytic cleavage of substrate in a pH-sensitive manner. The catalytic mechanism of BACE-1 requires water-mediated proton transfer from aspartyl dyad to the substrate, as well as structural flexibility in the flap region. Thus, the coupling of protonation and conformational equilibria is e...

background: l-tryptophan is used widespread in the pharmaceutical industry. the majority of l-trp production depends on microbial processes that produce l-tryptophan from indole and l-serine. these processes are very costly due to the costs of precursors, especially l-serine. use of inexpensive substitutions as the l-serine source of l-tryptophan production enables us to reach a cost-effective ...

abstract now, it’s completely proved that we can find strains among many strains of each rhizobial group that can also do effective process in plant growth promoting as plant growth hormones production (iaa), in addition of their ability in n2 fixation .therefore, the aim of this research is to determinate the ability of iaa production of some of the indigenous rhizobial strains by two quantita...

the dependence on ionic strength of protonation of glycine and its complexation with dioxouranium (vi) is reported in sodium perchlorate and sodium chloride solutions as background salts. the measurements have been performed at 25±0.1°c and various ionic strengths in the range 0.1 to 1.0 mol , using a combination of potentiometric and spectrophotometric techniques. the overall analysis  of the ...

Phosphotriesterase (PTE) is a binuclear metalloenzyme that catalyzes the hydrolysis of organophosphates, including pesticides and chemical warfare agents, at rates approaching the diffusion controlled limit. The catalytic mechanism of this enzyme features a bridging solvent molecule that is proposed to initiate nucleophilic attack at the phosphorus center of the substrate. X-band EPR spectrosco...