Neurospora enzyme

A portion of the DNA sequence of nit-6, the Neurospora gene encoding the enzyme nitrite reductase. (JaviesD. Cotandene, University of Virginia ... 

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... 

E. Physical Methods and Analytical Techniques.—Nucleotide maps of enzymic digests of DNA have been obtained using the same ionophoretic techniques as have been developed for RNA digests. Pancreatic DNase and Neurospora crassa endonuclease produce very similar maps with E. coli DNA but this technique still awaits the discovery of specific DNases. 

Effects of Allelochemlcals on ATPases. Several flavonoid compounds inhibit ATPase activity that is associated with mineral absorption. Phloretin and quercetin (100 pM) inhibited the plasma membrane ATPase Isolated from oat roots (33). The naphthoquinone juglone was inhibitory also. However, neither ferulic acid nor salicylic acid inhibited the ATPase. Additional research has shown that even at 10 mM salicylic acid inhibits ATPase activity only 10-15% (49). This lack of activity by salicylic acid was substantiated with the plasma membrane ATPase Isolated from Neurospora crassa (50) however, the flavonols fisetln, morin, myricetin, quercetin, and rutin were inhibitory to the Neurospora ATPase. Flavonoids inhibited the transport ATPases of several animal systems also (51-53). Thus, it appears that flavonoids but not phenolic acids might affect mineral transport by inhibiting ATPase enzymes. 

For nitrate reductase, evidence on the role of molybdenum in the catalytic mechanism of the enzyme from Neurospora was first presented in 1954 by Nicholas and Nason (21) and the position seems to have changed relatively little since then. The original conclusion (23) was that molybdenum functions as an electron carrier in the sequence ... 

Aus Neurospora konnte auBerdem ein Enzym (Phosphoacetylglucos-aminmutase) angereichert werden, welches die Gleichgewichtseinstellung... 

The latter authors demonstrate in their latest paper101) that bluelight (under physiological conditions stimulating conidiation and LIAC) will depress nitrate reductase activity and increase the activity of the smaller subunit of the enzyme complex in Neurospora. It is therefore suggested to be a key enzyme for physiological bluelight action. 

Beadle and Tatum had found that irradiation of Neurospora spores produced mutants which were incapable of carrying out certain well-defined chemical reactions, and it was at first supposed that as a result of the destruction of a specific gene, the potentiality for producing a particular enzyme was completely lost. The "wild type" of Neurospora could propagate satisfactorily when biotin was the only vitamin-like substance supplied in the culture medium. Of the many mutant strains produced, however, one needed, in addition to biotin, the vitamin riboflavin. Without a supply of riboflavin in the culture medium this so-called "riboflavinless mutant" would not grow. Since riboflavin is a part of an enzyme system always found in Neurospora, it is an obligatory cell constituent and either has to be produced by the cells themselves (as in the wild type) or supplied exogenously in... 

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. 

Bacterial electrodes [11, 31, 33, 46, 48, 49, 60] In this type of electrode, a suspension of suitable bacteria is placed between the sensor proper and a dialysis membrane that prevents passage of high-molecular substances (see fig. 8.3). The sensor is usually a gas probe. In the simple types of bacterial electrode, the determinand is converted by a suitable strain of bacteria into a product sensed by the gas probe. Thus it is possible to determine arginine [46], glutamine [48],/.-aspartic acid [31],/.-histidine [60] and nitrate [33]. Hybrid bacterial - enzyme electrodes contain both a bacterial strain and a suitable enzyme. For example, an extract from ivingas Neurospora chossa can be used as a source of NAD nucleosidase and an Escherichia coli culture as a source of nicotinamide deaminase, so that the electrode responds to NAD [49] as a result of the series of reactions... 

This enzyme [EC 1.1.1.23] catalyzes the reaction of l-histidinol with two NAD+ to produce L-histidine and two NADH. L-Histidinal will also serve as a substrate for this protein. The Neurospora crassa enzyme will also catalyze the reactions of phosphoribosyl-AMP cyclohydrolase [EC 3.5.4.19] and phosphoribosyl-ATP pyrophosphatase [EC 3.6.1.31]. 

This enzyme [EC 1.1.1.3] catalyzes the reaction of homoserine with NAD(P) to produce aspartate 4-semialdehyde and NAD(P)H. NAD is the better of the two coenzymes with the yeast enzyme whereas NADP+ is preferred by the Neurospora enzyme. See also Aspartate Kinase... 

This enzyme [EC 3.5.4.19] catalyzes the hydrolysis of 5-phosphoribosyl-AMP to produce 5-(5-phospho-D-ribo-sylaminoformimino)-l-(5-phosphoribosyl)tmidazole-4-carboxamide. The enzyme isolated from Neurospora crassa can also catalyze the reactions of histidinol dehydrogenase and phosphoribosyl-ATP pyrophosphatase. 

Enzyme Systems. Carotenoid biosynthesis by crude cell-free preparations from Halobacterium cutirubrum 0-carotene), Phycomyces blakesleeanus mutants (/8-carotene), and a Neurospora crassa mutant (phytoene) has been demonstrated. Detailed studies of carotenogenic enzymes from tomato fruit... 

Wolf, E.C. Weiss, R.L. Acetylglutamate kinase. A mitochondrial feedback-sensitive enzyme of arginine biosynthesis in Neurospora crassa. J. Biol. Chem., 255, 9189-9195 (1980)... 

Rossi, M. Woodward, D.O. Enzymes of deoxythymidine triphosphate biosynthesis in Neurospora crassa mitochondria. J. BacterioL, 121, 640-647 (1975)... 

Joshua Lederberg, George W. Beadle, and Edward L. Tatum Physiology/Medicine One gene-one enzyme hypothesis from genetic studies of neurospora... 

Roboz, E Barratt, R.W., and Tatum, E.L. 1952. Breakdown of pectic substances by a new enzyme from Neurospora. J. Biol. Chem. 195 459-471. 

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