Nucleotides and Nucleic Acids

Kit, Saul

doi:10.1016/b978-0-12-299254-4.50008-x

Cited by 24 publications

(10 citation statements)

References 918 publications

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“…4). This alternative sequence to dTMP has o been suggested before, and depends upon the existence of a 666 + 72 functioning "X deaminase" which lacks direct support in evidence (7,13,16 separate sites. The metabolic conversion of Cdr to dUMP via dCMP deaminase activity, and consequent partial rectification of the (apparently) huge excess of Cdr in the system is not reasonable in view of the distinct sensitivity differences between Cdr and Udr in bleaching induction and effects on growth, and the lack of prevention of Udr-induced bleaching by Tdr, Cr, or Ur.…”

Section: Mr =-___ _mentioning

confidence: 99%

Pyrimidine Metabolism in Lemna minor

Frick¹

1978

Plant Physiol.

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Cytidine deoxyriboside (Cdr), uridine deoxyriboside (Udr), and guanosine deoxyriboside (Gdr), induce quantitative bleaching of the fronds of Lemns minor (duckweed) during growth in continuous light on photoheterotrophic medium. Cdr-induced bleaching is not accompanied by a reduction in frond multiplication rate, but Udr-and Gdr-induced bleaching is. Bleaching by Cdr is fully prevented by thymidine (Tdr), cytidine (Cr), or uridine (Ur), but The isolation of purine and pyrimidine auxotrophs in higher plants, with the possible exception of Arabidopsis (17), has not proven possible. This has restricted description of existing metabolic pathways to selective confirmation of certain enzyme activities and to the use of only certain types of tissues (1,4,7,20 (Fig. Ib).Cdr, Udr, and Gdr (Table I)

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Section: Mr =-___ _mentioning

confidence: 99%

Pyrimidine Metabolism in Lemna minor

Frick¹

1978

Plant Physiol.

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“…These enzymes have been extensively studied in micro-organisms (23, 1 lo), and research with the mammalian enzymes indicates that many of the controls are similar t o those found in micro-organisms (86,137). Figure 3 summarizes the reactions involved in the interconversions of pyrimidine nucleotides.…”

Section: Interconversions O F Pyrimidine Nucleotidesmentioning

confidence: 99%

“…The enzyme is widely distributed in animal tissues (23,86). Uridine kinase catalyzes the conversion of uridine t o UMP.…”

Section: )mentioning

confidence: 99%

A Review: Biological and Clinical Aspects of Pyrimidine Metabolism

1974

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Interest in pyrimidine nucleotide biosynthesis has stemmed largely from the importance of these molecules as components of nucleic acids. Regulation of pyrimidine biosynthesis has been most extensively investigated in micro-organisms in which cell division is effectively controlled by regulation of the activity of the enzymes of the d e n o v o pathway (77, 11 0). The relation between pyrimidine biosynthesis and cellular proliferation in mammals has become clearer with the accumulation of a considerable body of evidence which indicates that there is a close correlation between the activity of enzymes involved in pyrimidine biosynthesis and the rate of cellular proliferation.The d e n o v o pyrimidine biosynthetic pathway and the urea cycle b o t h utilize carbamyl phosphate, and important nitrogen carrier. The biosynthesis of pyrimidine and purine nucleotides are connected by a common intermediate, phosphoribosyl pyrophosphate (PRPP). In addition, pyrimidine nucleotides act as sugar and phospholipid carriers and are important in lipopolysaccharide biosynthesis. The importance of these interrelations is most forcibly emphasized b y certain clinical phenomena which will be discussed later. This paper will attempt t o review the broad biologic aspects of pyrimidine nucleotide biosynthesis. A detailed consideration of d e n o v o pyrimidine biosynthesis in eucaryotic cells is available in the recent review by Jones (81). Pyrimidine biosynthesis in procaryotes has been reviewed in depth by O'Donovan and Neuhard (1 10). PATHWAYS O F PYRIMIDINE NUCLEOTIDE BIOSYNTHESISIn cells from multicellular organisms, pyrimidine nucleotide biosynthesis can proceed b y two mechanisms. D e n o v o biosynthesis of uridylic acid proceeds from simple components such as carbon dioxide, a source of nitrogen (either ammonia or the amide nitrogen of glutamine), ATP, aspartate. and ribose in the form of phosphoribosyl p y r~p h o s~h a t e . A reutilization ("salvage") mechanism is also available t o cells.-.whereby preformed pyrimidine bases o r nucleosides can be converted t o the nucleotide by the addition of ribose phosphate or phosphate. DE NOVO MECHANISMD e n o v o biosynthesis of uridylic acid required six enzymatic steps (Fig. 1). In procaryotes one enzyme supplies the carbamyl phosphate required for both pyrimidine nucleotide and arginine biosynthesis. Consequently, aspartate transcarbamylase is the first enzyme unique to the d e n o v o pyrimidine pathway and an important locus for control of the pathway (77).In contrast, in ureotelic vertebrates, there are t w o carbamyl phosphate synthetases. The first, carbamyl phosphate synthetase I, is located in the inner membrane of the mitochondrion of the liver and also appears t o be present in small quantities in kidney and small intestine (82). The second, carbamyl phosphate syntlietase 11, has a more ubiquitous distribution and was first demonstrated t o be present in Ehrlich ascites cells (58,59) and in hematopoietic mouse spleen (75,143). This enzyme was originally difficult t o dete...

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“…(5) I n the term nucleotide the nitrogenous base, though usually a heterocyclic ring as a purine or a pyrimidine, may have a more simple structure such as glycinamide or an amino group itself. The commonly found bases in the nucleic acids are, in RNA, adenine, guanine, uracil and cytosine and in DNA, adenine, guanine, cytosine and thymine, and in addition 5-methyl cytosine is found particularly in plant DNA.…”

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confidence: 99%

PURINES, PYRIMIDINES & RELATED COMPOUNDS

Oberholzer¹

1976

Paper and Thin Layer Chromatography

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Nucleotides and Nucleic Acids

Cited by 24 publications

References 918 publications

Pyrimidine Metabolism in Lemna minor

Pyrimidine Metabolism in Lemna minor

A Review: Biological and Clinical Aspects of Pyrimidine Metabolism

PURINES, PYRIMIDINES & RELATED COMPOUNDS

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