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(2010) The Biosynthesis of Nucleotides.

Nucleotides, Purine Biosynthesis and Purine Catabolism. LEARNING POINTS Understand nucleosides* , nucleotides , and their …

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Sources of Drugs: Biological, marine, mineral and plant tissue cultures as sources of drugs;
Classification of Drugs: Morphological, taxonomical, chemical and pharmacological classification of drugs; Study of medicinally important plants belonging to the families with special reference to: Apocynacae, Solanaceae, Rutacease, Umbelliferae, Leguminosae, Rubiaceae, Liliaceae, Graminae, Labiatae, Cruciferae, Papaveraceae; Cultivation, Collection, Processing and Storage of Crude Drugs: Factors influencing cultivation of medicinal plants, Types of soils and fertilizers of common use. Pest management and natural pest control agents, Plant hormones and their applications, Polyploidy, mutation and hybridization with reference to medicinal plants. Quality Control of Crude Drugs: Adulteration of crude drugs and their detection by organoleptic, microscopic, physical, chemical and biological methods and properties. Introduction to Active Constituents of Drugs: Their isolation, classification and properties.
Systematic pharmacognostic study of the followings:
CARBOHYDRATES and derived products: agar, guar gum acacia, Honey, Isabagol, pectin, Starch, sterculia and Tragacanth; Lipids: Bees wax, Castor oil, Cocoa butter, Codliver oil, Hydnocarpus oil, Kokum butter, Lard, Linseed oil, Rice, Bran oil, Shark liver oil and Wool fat; RESINS: Study of Drugs Containing Resins and Resin Combinations like Colophony, podophyllum, jalap, cannabis, capsicum, myrrh, asafoetida, balsam of Tolu, balsam of Peru, benzoin, turmeric, ginger;
TANNINS: Study of tannins and tannin containing drugs like Gambier, black catechu, gall and myrobalan;
VOLATILE OILS: General methods of obtaining volatile oils from plants, Study of volatile oils of Mentha, Coriander, Cinnamon, Cassia, Lemon peel, Orange peel, Lemon grass, Citronella, Caraway, Dill, Spearmint, Clove, Fennel, Nutmeg, Eucalyptus, Chenopodium, Cardamom, Valerian, Musk, Palmarosa, Gaultheria, Sandal wood; Phytochemical Screening: Preparation of extracts, Screening of alkaloids, saponins, cardenolides and bufadienolides, flavonoids and leucoanthocyanidins, tannins and polyphenols, anthraquinones, cynogenetic glycosides, amino acids in plant extracts; FIBERS: Study of fibers used in pharmacy such as cotton, silk, wool, nylon, glass-wool, polyester and asbestos.
Study of the biological sources, cultivation, collection, commercial varieties, chemical constituents, substitutes, adulterants, uses, diagnostic macroscopic and microscopic features and specific chemical tests of following groups of drugs:
GLYCOSIDE CONTAINING DRUGS: Saponins : Liquorice, ginseng, dioscorea, sarsaparilla, and senega. Cardioactive glycosides: Digitalis, squill, strophanthus and thevetia, Anthraquinone cathartics: Aloe, senna, rhubarb and cascara, Others: Psoralea, Ammi majus, Ammi visnaga, gentian, saffron, chirata, quassia.
ALKALOID CONTAINING DRUGS: Pyridine-piperidine: Tobacco, areca and lobelia. Tropane: Belladonna, hyoscyamus, datura, duboisia, coca and withania. Quinoline and Isoquinoline: Cinchona, ipecac, opium. Indole: Ergot, rauwolfia, catharanthus, nux-vomica and physostigma. Imidazole: Pilocarpus. Steroidal: Veratrum and kurchi. Alkaloidal Amine: Ephedra and colchicum. Glycoalkaloid: Solanum. Purines: Coffee, tea and cola. Biological sources, preparation, identification tests and uses of the following enzymes: Diastase, papain, pepsin, trypsin, pancreatin. Studies of Traditional Drugs: Common vernacular names, botanical sources, morphology, chemical nature of chief constituents, pharmacology, categories and common uses and marketed formulations of following indigenous drugs: Amla, Kantkari, Satavari, Tylophora, Bhilawa, Kalijiri, Bach, Rasna, Punamava, Chitrack, Apamarg, Gokhru, Shankhapushpi, Brahmi, Adusa, Atjuna, Ashoka, Methi, Lahsun, Palash, Guggal, Gymnema, Shilajit, Nagarmotha and Neem. The holistic concept of drug administration in traditional systems of medicine. Introduction to ayurvedic preparations like Arishtas, Asvas, Gutikas, Tailas, Chumas, Lehyas and Bhasmas.
General Techniques of Biosynthetic Studies and Basic Metabolic Pathways/Biogenesis: Brief introduction to biogenesis of secondary metabolites of pharmaceutical importance. Terpenes: monoterpenes, sesquiterpenes, diterpenes, and triterpenoids. Carotenoids: a-carotenoids, ß-carotenes, vitamin A, Xanthophylls of medicinal importance. Glycosides: Digitoxin, digoxin, hecogenin, sennosides, diosgenin and sarasapogenin. Alkaloids: Atropine and related compounds, Quinine, Reserpine, Morphine, Papaverine, Ephedrine, Ergot and Vinca alkaloids. Lignans, quassanoids and flavonoids. Role of plant-based drugs on National economy: A brief account of plant based industries and institutions involved in work on medicinal and aromatic plants in India. Utilization and production of phyto-constituents such as quinine, calcium sennosides, podophyllotoxin, diosgenin, solasodine, and tropane alkaloids. Utilization of aromatic plants and derived products with special reference to sandalwood oil, mentha oil, lemon grass oil, vetiver oil, geranium oil and eucalyptus oil. World-wide trade in medicinal plants and derived products with special reference to diosgenin (disocorea), taxol (Taxus sps) digitalis, tropane alkaloid containing plants, Papain, cinchona, Ipecac, Liquorice, Ginseng, Aloe, Valerian, Rauwolfia and plants containing laxatives. Plant bitters and sweeteners. Plant Tissue Culture: Historical development of plant tissue culture, types of cultures, nutritional requirements, growth and their maintenance. Applications of plant tissue culture in pharmacognosy. Marine pharmacognosy: Novel medicinal agents from marine sources. Natural allergens and photosensitizing agents and fungal toxins. Herbs as health foods. Herbal cosmetics. Standardization and quality control of herbal drugs, WHO guidelines for the standardization of herbal drugs.

Purines, Pyrimidines and Nucleotides and the Chemistry of Nucleic Acids serves as an ..

With the exception of the discussions of purine and pyrimidine nucleotidedegradation, which are generalized to ribonucleotides and deoxyribonucleotides,the biosynthetic pathways that we have looked at were specific toribonucleotides and, therefore, to RNA. Now we want to build upon this todiscuss the components of DNA, the deoxyribonucleotides.

The Biosynthesis of Nucleotides

What this shows is that the overall effect of combining these two reactionsis a net result of deaminating an aspartate to a fumarate at the expense of aGTP molecule. This cycle of reactions is know as the and it is ofphysiologic importance in muscle metabolism. Muscle tissue replenishes itscitric acid cycle intermediates via the purine nucleotide cycle rather thanthrough the usual "replenishing reactions", the most important ofwhich is the generation of oxaloacetate from pyruvate catalyzed by pyruvatecarboxylase. The fumarate generated in the purine nucleotide cycle feeds intothe citric acid cycle to regenerate malate, oxaloacetate, and so forth.

What's really interesting here is that the ribose sugar is recycled in theform of ribose-1-phosphate, which can be incorporated into PRPP which, as we nowknow, is integral to the biosynthesis of purines, pyrimidines, histidine andtryptophan. That's a really efficient way to run a cell!

The Biosynthesis of Purine Nucleotides

Biosynthesis of nucleotides is under tight regulatory control in the cell. Organisms need to make just the right amount of each base; if too much is made, energy is wasted, if too little, DNA replication and cellular metabolism come to a halt. Also, the cell is sensitive to the presence of any premade nucleotides in its environment and will down regulate their synthesis pathways in favor of using what is already present in the surroundings. Bacteria are capable of interconverting purines (adenine and guanine) and interconverting pyrimidines (thymidine, cytidine and uracil). If a growth medium provides a purine and a pyrimidine, many microbes are capable of synthesizing the other needed nucleotides from them.

We expected that the first step, in which PRPP is synthesized, would besubject to regulation because of the prominence of PRPP in other biosyntheticreactions, including that of pyrimidine nucleotides. Increasing levels of ADPand GDP have a negative feedback effect on the enzyme Ribose phosphatepyrophosphokinase. The enzyme catalyzing the second step of the pathway,Amidophosphoribosyl transferase, is inhibited by all of the adenine and guaninenucleotides, the adenine nucleotides binding to one inhibitory site on theenzyme and the guanine nucleotides to another separate site. This enzyme is also"activated" by the increase in the level of PRPP and this is called a"feedforward activation".

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Synthesis of Purine Nucleotides,gout

When ATP appears as a reactant, it can generally participate in two ways:part of the ATP molecule can be transferred to an acceptor molecule or ATPhydrolysis can drive an otherwise unfavorable reaction. The Pi, PPi,adenyl or adenosinyl groups can be transferred, as in the first step in thepurine biosynthetic pathway. In such instances, the substrate is said to be"activated" by the transfer. When the free energy of ATP hydrolysisdrives an endergonic reaction, the overall mechanism must involve transfer of aPi group somewhere along the way, even though, in the final analysis,it will appear as Pi in the reaction ATP + H20 -->ADP + Pi. Otherwise, there would be no way to couple thereactions.

the biosynthesis of purine nucleotides.

The basic idea here is that there is exquisite control of the amounts ofpurine nucleotides available for synthesis of nucleic acids, and that thepathways are individually regulated at the cellular level. Furthermore, therelative amounts of ATP and GTP are also controlled at the cellular level.

BIOSYNTHESIS OF NUCLEOTIDES IN WHEAT: I. PURINES …

We will see that all purine nucleotides are ultimately degraded to uric acid,which is itself a purine. Studies by Buchanan in the mid 1900s established theorigin of the individual atoms in uric acid, and it's helpful to mention thesenow, as we will soon see how they are incorporated into the molecule. Using thenumbering convention as described, we will see the following:

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