Peptidoglycan types of bacterial cell walls and their taxonomic implications.

The preparation and enzymatic hydrolysis of reduced and S-carboxymethylated proteins.

Although vitamin E has been known as an essential nutrient for reproduction since 1922, we are far from understanding the mechanisms of its physiological functions. Vitamin E is the term for a group of tocopherols and tocotrienols, of which alpha-tocopherol has the highest biological activity. Due to the potent antioxidant properties of tocopherols, the impact of alpha-tocopherol in the prevention of chronic diseases believed to be associated with oxidative stress has often been studied, and beneficial effects have been demonstrated. Recent observations that the alpha-tocopherol transfer protein in the liver specifically sorts out RRR-alpha-tocopherol from all incoming tocopherols for incorporation into plasma lipoproteins, and that alpha-tocopherol has signaling functions in vascular smooth muscle cells that cannot be exerted by other forms of tocopherol with similar antioxidative properties, have raised interest in the roles of vitamin E beyond its antioxidative function. Also, gamma-tocopherol might have functions apart from being an antioxidant. It is a nucleophile able to trap electrophilic mutagens in lipophilic compartments and generates a metabolite that facilitates natriuresis. The metabolism of vitamin E is equally unclear. Excess alpha-tocopherol is converted into alpha-CEHC and excreted in the urine. Other tocopherols, like gamma- and delta-tocopherol, are almost quantitatively degraded and excreted in the urine as the corresponding CEHCs. All rac alpha-tocopherol compared to RRR-alpha-tocopherol is preferentially degraded to alpha-CEHC. Thus, there must be a specific, molecular role of RRR-alpha-tocopherol that is regulated by a system that sorts, distributes, and degrades the different forms of vitamin E, but has not yet been identified. In this article we try to summarize current knowledge on the function of vitamin E, with emphasis on its antioxidant vs. other properties, the preference of the organism for RRR-alpha-tocopherol, and its metabolism to CEHCs.

http://tocofemax.com.br/site/artigos/1.pdf

Vitamin E: function and metabolism

This article summarizes all experimental facts concerning the cold denaturation of single-domain, multi-domain, and multimeric globular proteins in aqueous solutions with and without urea and guanidine hydrochloride. The facts obtained by various experimental techniques are analyzed thermodynamically and it is shown that the cold denaturation is a general phenomenon caused by the very specific and strongly termperature-dependent interaction of protein nonpolar groups with water. Hydration of these groups, in contrast to expectations, is favorable thermodynamically, i.e., the Gibbs energy of hydration is negative and increases in magnitude at a temperature decrease. As a result, the polypeptide chain, tightly packed in a compact native structure, unfolds at a sufficiently low temperature, exposing internal nonpolar groups to water. The reev-aluation of the hydration effect on the base of direct calorimetric studies of protein denaturation and of transfer of non-polar compounds into water leads to r...

Cold denaturation of proteins.

https://mmbr.asm.org/content/mmbr/49/1/81.full.pdf

Polyamines in microorganisms.

The enzymatic oxidation of pyridoxine and pyridoxamine phosphates.

Publisher Summary This chapter examines some of these questions with respect to vitamin B6. The problem can be considered from three points of view: (1) what are the structural features required for vitamin B6 activity in living organisms, (2) what structural features determine the ability of a compound to serve as a coenzyme for vitamin B6-dependent enzymes, and (3) apart from ability to combine with its conjugate apoenzymes, what chemical features determine the ability of the coenzyme to participate in catalysis of the reactions for which it is essential? These questions can be profitably considered in reverse order because unless the chemical prerequisites for participation in catalysis are present, a compound obviously will be of no value as a coenzyme, however closely it may resemble the coenzyme in other respects. By the same token, it cannot serve as a vitamin, the sole function of which is to serve as a precursor for coenzyme formation.

Esmond E. Snell

Papers

The enzymatic oxidation of pyridoxine and pyridoxamine phosphates.

Chemical structure in relation to biological activities of vitamin B6.

Pyridoxal phosphokinases. I. Assay, distribution, I. Assay, distribution, purification, and properties.

Properties of Crystalline Tryptophanase

The relation of spectral changes and tritium exchange reactions to the mechanism of tryptophanase-catalyzed reactions.