PPT - Metabolism of purines and pyrimidines …
Dietary EAA deficiencies may arise from the leaching of free and proteinbound amino acids into the water. For example, Grabner, Wieser and Lackner(1981) reported the loss, through leaching, of almost all the free and aboutone-third of the free plus protein bound amino acids from frozen or freezedriedzooplankton (Artemia salina and Moina spp.) after a 10 minute waterimmersion period at 9°C. Considerable losses of water-soluble amino acidshave also been observed in carp during mastication (Yamada and Yone, 1986).However, the problem of nutrient leaching of water soluble materials isprobably greatest for crustaceans due to their very slow demersal feedinghabit and necessity to masticate their food externally prior to ingestion(Farmanfarmaian, Lauterio and Ibe, 1982). For example, Bages and Sloane (1981)reported a 28% loss of dietary protein during the preparation and rehydrationof a dry alginate-bound shrimp diet prior to feeding, and a total protein lossof 39–47% after a six hour immersion period in seawater. In general nutrientlosses are greater in freshwater than in seawater (Balazs, Ross and Brooks,1973). However, problems of nutrient leaching can be minimised by using anappropriate feeding regime (ie. regular rather than infrequent feeding;Sedgwick, 1979) and a suitable diet binding or micro-encapsulation technique(Goldblatt, Conklin and Duane Brown, 1980; Jones et al., 1976).
Structure of purine and pyrimidine nucleotides
As a guide line Table 4 presents the calculated dietary EAA requirements of fishand shrimp at varying dietary protein levels based on the mean carcass EAA patternof whole fish tissue and short-necked clam tissue respectively (short-necked clamtissue is used here in the absence of a mean carcass EAA pattern for shrimp).
On the basis of the above discussions it is evident that the protein qualityof a feed ingredient is dependent upon the amino acid composition of the proteinand the biological availability of the amino acids present. In general, the closerthe EAA pattern of the protein approximates to the dietary EAA requirement of thespecies, the higher its nutritional value and utilization. For example, Table 5presents the ‘chemical score’ or potential protein value of some commonly usedfeed proteins. Chemical scores of 100 indicate that the level of a particularEAA within the feed protein is identical to the dietary EAA requirement level forfish (when expressed as a percentage of the total EAAs plus cystine and tyrosine)as determined by Ogino (1980a). The chemical score of the protein is taken tobe the percentage of the EAA in greatest deficit relative to the dietary requirementpattern. This method of assessing protein quality is based on the concept thatthe nutritive value of a protein depends primarily on the amount of the EAA ingreatest deficit in that protein, compared to a reference protein (in this casethe reference protein is the dietary EAA requirements of fish as determined byOgino. 1980a). It can be seen from Table 5 that compared to fish meal or fishmuscle, which has a well balanced EAA profile and high chemical score (c. 80),the majority of protein sources presented have amino acid imbalances which renderthem unsuitable as a sole source of dietary protein for fish within completediets intended for intensive farming systems. The aim of feed formulation is tomix proteins of various qualities to obtain the desired EAA pattern of the fishor shrimp species in question (complete diet feeding).
The Metabolism of Purines and Pyrimidines | …
The porphyrins, purines and pyrimidines are compounds with nitrogen-containing heterocyclic ring systems essential to the primary biochemical processes which maintain life. Without the porphyrin derivative, chlorophyll, there would be no de novo synthesis of sugars and therefore no energy to carry out the biochemical reactions of higher plants and animals. The nucleic acids, derivatives of purines and pyrimidines, are even more important to life, as without these compounds there would be no replication of protein molecules and no transmittance of heredity. Porphyrins, purine and pyrimidine derivatives are also involved in the prosthetic groups of many enzymes. A prosthetic group is the non-protein component of an enzyme which is firmly bound to the protein or apoenzyme, the complete complex forming a haloenzyme. More loosely bound non-protein components are known as coenzymes. A purine derivative is involved in the important complex, coenzyme A.
What's the difference between Purines and Pyrimidines
FOLINIC ACID, which also is known as 5-formyl tetrahydrofolate, is one active form in a group of vitamins known as folates. In contrast to folic acid, a synthetic form of folate, folinic acid is one of the forms of folate found naturally in foods. Folate deficiency is believed to be the most common vitamin deficiency in the world due to food processing, food selection, and intestinal disorders. Folinic acid in the body can be converted into any of the other active forms of folate.
Folinic Acid contains 800 mcg of folinic acid from a very pure form of calcium folinate. It is contained in a small gelatin capsule only with microcrystalline cellulose (filler) and silica (flow agent). It contains no magnesium stearate.
Nucleotide Metabolism: Nucleic Acid Synthesis
Folate coenzymes are responsible for the following important metabolic functions and benefits: 1) Formation of purines and pyrimidines, which in turn are needed for synthesis of the nucleic acids DNA and RNA. This is especially important during fetal development in the first trimester in preventing birth defects, such as neural tube defects, 2) Formation of heme, the iron-containing protein in hemoglobin, 3) Interconversion of the 3-carbon amino acid serine from the 2-carbon amino acid glycine, 4) Formation of the amino acids tyrosine from phenylalanine and glutamic acid from histidine, 5) Formation of the amino acid methionine from homocysteine (Vitamin B12 as also is needed for this conversion). In the reconversion of homocysteine to methionine the body uses the methionine to make the important amino acid s-adenosylmethionine (SAMe) which is known to be helpful in cases of depression, 6) Synthesis of choline from ethanolamine, 7) Formation and maturation of red and white blood cells, and 8) Conversion of nicotinamide to N’-methylnicotinamide.