New yellow enzyme

New Yellow Enzyme. Shortly after the isolation of the old yellow enzyme, Haas, in Warburg s laboratory, isolated a second flavoprotein from yeast. This enzyme, the new yellow enzyme differs from the... 

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. 

Application of the Bioreduction System to Other Cofactor-Dependent Enzyme Reactions Discovery of New Functions of Old Yellow Enzymes... 

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)... 

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. 

Two cofactors were found to be essential for the production of hydrogenobyrinic acid 60 from precorrin-3A 55, namely SAM, as would be expected, but also reduced nicotinamide adenine dinucleotide phosphate (NADPH, partial structure 59) which was surprising. Scheme 19. Omission of NADPH from the incubation gave a critically important result no 60 was formed but a new pale-yellow product appeared in its place. When a labelled form of this new pigment was incubated with the enzyme system, now with NADPH included, it was specifically converted into hydrogenobyrinic acid 60 in high yield. Clearly, a new intermediate for Bi2-biosynthesis had been found which opened the door to dramatic progress [89]. 

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