Modeling of alcohol oxidase enzyme of Candida boidinii and in silico analysis of competitive binding of proton ionophores and FAD with enzyme

Structure-Guided Evolution Modulate Alcohol Oxidase to Improve Ethanol Oxidation Performance

A high ethanol usage of alcohol oxidase (AOX) was required in industry. In this study, a "expand substrate pocket" strategy achieved a high activity AOX from Hansenula polymorpha (H. polymorpha) by Phe to Val residue (F/V) site-directed mutation to enlarge ethanol channel. Although H. Polymorpha AOX (HpAOX) possessed respectively 71.3% and 76.1% similarity with AOX (PpAOX) from Pichia pastoris (P. pastoris) in DNA and protein sequences, their active site structures including catalytic site and substrate channel were similar according to computer-aided analysis. After 3D structure analysis, Phe99 residue of their substrate channels was the most important residue to impact enzyme activity because of its large aromatic side chains. F99V mutation of HpAOX (HpAOXF99V) was designed and executed based on the enzyme catalytic mechanism and molecular computation in order to allow more larger size ethanol into active site. The highest enzyme activity of the fourth strains of HpAOXF99V mutant strain exhibited 12.06-folds increase than that of the host GS115 strain. Furthermore, kinetic studies indicated that the HpAOXF99V significantly promoted catalytic efficiency of ethanol than HpAOX, including Km, Vmax, kcat and kcat/Km. We also provided a new insight that the cofactor FAD irritated both active AOX octamer biosynthesis production and enzyme-catalysed ability due to help enzyme assembly and redox potential.

Vanadate inhibits Feo-mediated iron transport in Vibrio cholerae

Iron is an essential element for Vibrio cholerae to survive, and Feo, the major bacterial system for ferrous iron transport, is important for growth of this pathogen in low-oxygen environments. To gain insight into its biochemical mechanism, we evaluated the effects of widely used ATPase inhibitors on the ATP hydrolysis activity of the N-terminal domain of V. cholerae FeoB. Our results showed that sodium orthovanadate and sodium azide effectively inhibit the catalytic activity of the N-terminal domain of V. cholerae FeoB. Further, sodium orthovanadate was the more effective inhibitor against V. cholerae ferrous iron transport in vivo. These results contribute to a more comprehensive biochemical understanding of Feo function, and shed light on designing effective inhibitors against bacterial FeoB proteins.

A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation

Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.

Fully edible biofuel cells

This article describes the first example of edible energy harvesting biofuel cells, based solely on highly biocompatible and ingestible food materials.