New yellow enzyme and

The attention of biochemists was first attracted to flavins as a result of their color and fluorescence. The study of spectral properties of flavins (Fig. 15-8) has been of importance in understanding these coenzymes. The biochemical role of the flavin coenzymes was first recognized through studies of the "old yellow enzyme"144 145 which was shown by Theorell to contain riboflavin 5 -phosphate. By 1938, FAD was recognized as the coenzyme of a different yellow protein, D-amino acid oxidase of kidney tissue. Like the pyridine nucleotides, the new flavin coenzymes were reduced by dithionite to nearly colorless dihydro forms (Figs. 15-7 and 15-8) revealing the chemical basis for their function as hydrogen carriers. 

The generation of stereogenic centers by asymmetric reduction of carbon-carbon double-bonds is a current topic in chemoenzymatic synthesis. Though enzymes of the old yellow enzyme (OYE) family were identified to perform alkene reduction and were characterized some years ago [133-135], applications of enoate reductases in natural product syntheses are still rare. Thus, potential applications are also shown in this chapter. With an increasing number of new enoate reductases, such as YqjM reductase from B. subtilis, more and more possible targets for biotransformations can be found. 

The discovery of iron led rapidly to the use of spectroscopic techniques to study the behavior of this metal, especially in LOX-1. De Groot et al. (1975), and later Pistorius and Axelrod (1976), found that incubating the colorless native enzyme (LOX-1) with a stoichiometric amount of 13-LOOH resulted in the formation of a yellow enzyme (A ax = 300 nm at pH 9.0 360 nm at pH 7.1). The formation of this new species results in the loss of LOX fluorescence (Amax = 330 nm, excitation at 280 nm) in the presence of 1 mol of 13-LOOH (Finazzi-Agro et al., 1973). Upon the addition of a large excess of 13-LOOH to the native or yellow enzyme, a purple species (A ax = 570 nm)... 

This paper used a combinatorial method of enzyme and chemical method to extract dietary fiber from Sargassum fusiforme. The optimal combination were mass ratio of trypsin and cellulose as 30 1, hydrolysis temperature as 40°C and hydrolysis time as 1.5 h, 2.5% NaOH with 30 volume, NaOH extraction temperature as 65°C and extraction time as 2h.The yield of dietary fiber could reach 23%. The product was light yellow and could be a supplement source of dietary fiber. This study provided a new process for the comprehensive utilization of Sargassum fusiforme. 

In Theorell s first experiment, the yellow enzyme left the membrane J with a fairly sharp rear which could be observed visually due to the color of the enzyme. It penetrated filter paper K, and, in the chamber G, the specifically heavier enzyme solution sedimented to the bottom, to the impermeable membrane L, where it formed a layer of concentrated solution. After the color had completely left the upper cell, a new lot of the mixture could be introduced through tube 1, and simultaneously the same volume of impurities were withdrawn through tube 3. 

More than 100 years ago a fluorescent compound was isolated first fi om whey, and later from different biological materials. When it Ijecame clear that the isolated yellow pigments, named lactochrome, ovoflavin, or lactoflavin, had a common structure, the new compound was named riboflavin (vitamin B2) (for historical review see 2). In the years between 1933 and 1935 the structure and the main chemical reactions of riboflavin were studied and the chemical synthesis was performed. Soon afterward, the coenzyme forms, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), were isolated in pure form, and the structures were determined. In the last 50 years many flavoproteins were isolated and their physicochemical properties were studied. Succinate dehydrogenase was the first enzyme found with the prosthetic group (FAD) covalently bound to the protein. About 20 flavoproteins are now known to contain covalently bound coenzyme (mainly via carbon atom 8a) (3). In mammalian tissue, the number of covalently bound flavoproteins appears to be limited. 

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