Organisms Neurospora

Lysine.—Lysine is a common precursor of piperidine alkaloids. Of the two enantiomers of this amino-acid, the L-isomer is the more direct precursor, in plants, for piperidine alkaloids, e.g. anabasine, whereas D-lysine is more directly implicated in the biosynthesis of pipecolic acid (24)1,2,23 (cf Vol. 7, p. 7). It has now been shown that a pathway exists in the plant Nicotiana glauca,24 and also in the micro-organism Neurospora crassa2S which transforms D-lysine into L-lysine by way of L-pipecolic acid (24). 

The sequence omithine-citrulline-arginine, first shown to occur in mammalian liver, has been found in many other organisms Neurospora, PenidUium, E. coU, lactobacilli, animal tissues, etc.). 

Neurospora crassa is a filamentous pink mould. It became famous to scientists due to the work of Beadle and Tatum in the 1940s when they developed the one gene—one enzyme hypothesis. Its life cycle is shown in Fig. 2.9. Unforturrately, the full force of fungal nomenclature comes into play when considering this organism. Aerial hyphae... 

However, Phinney (8) has suggested on the basis of experiments with mutants of Neurospora that the biosynthesis of cysteine involves the coupling of sulfate with an organic compound (presumably cysteine sulfinic acid) followed by reduction to sulfide. He noted also that sulfate may be reduced stepwise to sulfide and may then enter the protein as such. But he observed this process proceeds less readily than when sulfate combines first with protein. 

AsnRS was first characterized in the early 1960s in L. arabimsus hy its distinct chromatographic properties from aspartyl-tRNA synthetase and Asn synthetase and, at the end of the decade in E. coli as a protein of 90-100 kDa able to aminoacylate tRNA but not tRNA f / ° The enzyme was further characterized in mitochondria from Neurospora crassa" and in rat liver where tRNA asparaginylation activity was found associated with proteins of Air 35 and 90 kDa. The AsnRS purified from B. stearothermophilus of 127 kDa was characterized as a homodimer az (a = 51 kDa).AsnRSs isolated until now from various prokaryotic and eukaryotic organisms show conservation of the homodimeric structure. Investigation of B. stearothermophilus AsnRS allowed the determination of its physicochemical parameters S2o a = 6.6 x 10 s. 

Positive results from the gene mutation test in Neurospora crassa indicate that the test substance causes mutations in the DNA of this organism. 

Kolmark, G. Giles, N.H. (1955) Comparative studies of monoepoxides as inducers of reverse mutations in Neurospora. Genetics, 40, 890-902 Lide, D.R. Milne, G.W.A. (1996) Properties of Organic Compounds, Version 5.0, Boca Raton, FL, CRC Press [CD-ROM]... 

The recognition that the Mo in the molybdoproteins exists in organic cofactor forms came from studies of mutants of Aspergillus and Neurospora.650 In 1964, Pateman and associates discovered mutants that lacked both nitrate reductase and xanthine dehydrogenase. Later, it was shown that acid-treated molybdoenzymes released a material that would restore activity to the inactived nitrate reductase from the mutant organisms. This new coenzyme, a phosphate ester of molybdopterin (Fig. 15-17), was characterized by Rajagopalan and coworkers.650 651 A more complex form of the coenzyme, molybdopterin cytosine dinucleotide... 

Among different organisms the five enzyme activities required for tryptophan synthesis are distributed on different proteins (table 21.1). For example, in E. coli, indoleglycerol phosphate synthase catalyzes both the isomerization of phosphoribosylanthranilate and the cyclization step. Of particular interest is the occurrence of a single protein of the catalytic activities for nonconsecutive reactions in some cases. If in such cases the proteins were separate from each other in the cell, this arrangement, for example, in Neurospora, would necessitate the product of one reaction leaving the product site of one enzyme to be acted on by another... 

Prior to 1941, mj/o-inositol was often determined by isolation, as such or as the hexaacetate.87 The isolated inositol was weighed, or was oxidized to carbon dioxide (which was measured in a gas buret).92 In 1941, Woolley98 published his microbiological method, in which the yeast Saccharomyces cerevisiae was used as a test organism. Soon afterward, there appeared an improved procedure, using Saccharomyces carlsbergensis,9i 96 and an additional method based on the discovery of an inositol-less mutant of the common bread-mold, Neurospora crassa.96-98 Plundreds of types of foods,... 

Fig. 10.3 Amino acid sequences of CuZn-SODs from various organisms.31 Yeast, Saccharomyces cerevisiae Neurospora, Neurospora crassa Arabido., Arabidopsis thaliana Cyt, cytosolic CuZn-SOD Chi, chloroplastic CuZn-SOD. Amino acid residue number is based on that of human CuZn-SOD. Residues conserved in all species are boxed.

What may be called the 3-deoxy-D-om6mo-heptulosonic acid 7-phosphate pathway is used in E. coli for the synthesis of (a) the aromatic amino acids of proteins and (b) p-aminobenzoate. In Neurospora this pathway is also used for the synthesis of niacin ( > since these organisms convert tryptophan to niacin by a pathway first observed in mammals, but E. coli synthesizes niacin by a different pathway. jt is clear at present, even on the basis of limited evidence, that plants use the 3-deoxy-D-oroWno-heptulosonic acid 7-phosphate pathway for the synthesis of a much more extensive series of products. 

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