Biosynthesis vitamins

Folic acid - [FOOD TOXICANTS, NATURALLY OCCURRING] (Volll) - [FINECHEMICALS - PRODUCTION] (Vol 10) -m animal nutrition [VITAMINS - FOLIC ACID] (Vol 25) -biosynthesis [VITAMINS - FOLIC ACID] (Vol 25) -m dairy substitutes [DAIRY SUBSTITUTES] (Vol 7) -deficiency [VITAMINS - FOLIC ACID] (Vol 25) -metabolism of [VITAMINS - FOLIC ACID] (Vol 25) -metabolites [VITAMINS - FOLIC ACID] (Vol 25) -mmilk [MILKANDMILKPRODUCTS] (Vol 16) -one-pot synthesis [VITAMINS - FOLIC ACID] (Vol 25) -properties [VITAMINS - FOLIC ACID] (Vol 25) -role m veterinary medicine [VETERINARY DRUGS] (Vol 24)... 

CYP27 3 3 Bile acid biosynthesis, vitamin D3 hydroxylations... 

SmirnoffN (2001) L-Ascorbic acid biosynthesis. Vitamins arui Hormones 61,241-66. 

Several laboratories have been concerned with the effect of ascorbic acid deficiency on amino acid metabolism. Two main aspects have been investigated (1) a rather unspecific effect on the amino acid content in muscle and in blood and (2) a more specific action of vitamin C on the hydroxylation of some amino acids or intermediates in amino acid biosynthesis. Vitamin C deficiency alters the ratio of the various amino acid concentrations in muscle and blood. In muscle, while glutamic acid, leucine, valine, and methionine levels increase, glutamine and aspartic acid concentrations decrease. In blood of scorbutic guinea pigs, the concentrations of most of the amino acids decrease, while phenylalanine, leucine, and histidine levels rise. There is no definite explanation for these changes they indicate only that ascorbic acid is directly or indirectly involved with amino acid metabolism. 

Vitamin Bg is essential for more than 100 enzymes involved in protein metabolism. Pyridoxal-5 -phosphate is covalently bound to enzymes via a SchifFs base with an e-amino group of lysine in the enzyme. PLP-dependent enzymes are involved in important steps of amino acid metabolism, hemoglobin formation and chlorophyll biosynthesis. Vitamin Bg could have a role in preventing oxidative stress of the cells and is an impotent quencher of singlet oxygen. 

Vitamin Bj 2 is concerned in the biosynthesis of methyl groups of choline and methionine. 

Many kinds of amino acids (eg, L-lysine, L-omithine, t-phenylalanine, L-threonine, L-tyrosine, L-valine) are accumulated by auxotrophic mutant strains (which are altered to require some growth factors such as vitamins and amino acids) (Table 6, Primary mutation) (22). In these mutants, the formation of regulatory effector(s) on the amino acid biosynthesis is genetically blocked and the concentration of the effector(s) is kept low enough to release the regulation and iaduce the overproduction of the corresponding amino acid and its accumulation outside the cells (22). 

L-Ascorbic acid biosynthesis in plants and animals as well as the chemical synthesis starts from D-glucose. The vitamin and its main derivatives, sodium ascorbate, calcium ascorbate, and ascorbyl palmitate, are officially recognized by regulatory agencies and included in compendia such as the United S fates Pharmacopeia/National Formula (USP/NF) and the Food Chemicals Codex (FCC). 

In nature, vitamin A aldehyde is produced by the oxidative cleavage of P-carotene by 15,15 - P-carotene dioxygenase. Alternatively, retinal is produced by oxidative cleavage of P-carotene to P-apo-S -carotenal followed by cleavage at the 15,15 -double bond to vitamin A aldehyde (47). Carotenoid biosynthesis and fermentation have been extensively studied both ia academic as well as ia iadustrial laboratories. On the commercial side, the focus of these iavestigations has been to iacrease fermentation titers by both classical and recombinant means. 

The study of the biosynthesis of vitamin B 2 is a saga whose resolution, due primarily to Battersby (80—83) and Scott (84,85), requited an effort on the same magnitude as the total synthesis. It was only when recent molecular biology tools became available to complement en2ymology, isotopic labeling, chemical synthesis, and spectroscopy that solution of this problem became possible. 

Animals caimot synthesize the naphthoquinone ring of vitamin K, but necessary quantities are obtained by ingestion and from manufacture by intestinal flora. In plants and bacteria, the desired naphthoquinone ring is synthesized from 2-oxoglutaric acid (12) and shikimic acid (13) (71,72). Chorismic acid (14) reacts with a putative succinic semialdehyde TPP anion to form o-succinyl benzoic acid (73,74). In a second step, ortho-succmY benzoic acid is converted to the key intermediate, l,4-dihydroxy-2-naphthoic acid. Prenylation with phytyl pyrophosphate is followed by decarboxylation and methylation to complete the biosynthesis (75). 

---