Biochemistry

Daily intake of vitamin Вб for adults is on average 2-3 mg. It increases with severe physical exertion, neuropsychic stress, when working with radioactive substances and pesticides, with radiation injuries, as well as skin diseases, kidney, intestinal, anemia, antibiotic treatment, toxicosis of pregnant women, breast ­ feeding mothers. Need for vitamin B 6 increases with an increase in the amount of protein in the diet. Sources. Meat, fish, By-products (especially the liver and kidneys), egg yolks, as well as peas, yeast, bran are rich to vitamin B 6 . This vitamin is found in the shell of grain. During the processing of grain, up to 80% of pyridoxine is lost. Vitamin Be is destroyed by frying and smoking (up to 50%). A certain part of this vitamin is synthesized in the body of a healthy person due to the colon microflora. Cyanocobalamin (vitamin B 12 , antianemic factor). Vitamin B] 2 the first time in a crystalline state was obtained in 1948. Due to the complex structure, its chemical structure was deciphered only in 1953, and its synthesis was carried out in 1971. Structure and physicochemical properties. There are two parts in the vitamin B )2 molecule: cobalt-containing (corrinoid-porphyrin-like, or chromoform-like) and nucleotide-containing, i.e. it consists of the so-called planar group, which contains reduced pyrrole rings v/ith a Co atom in the center, and a nucleotide group perpendicular to it, the basis of which is dimethylbenzimidazole, and the ribose residue as the carbohydrate component (Fig. 12.1 ). Cyanocobalamin is resistant to high temperature. At a pH of 5.0-4.5, it can withstand even sterilization. Vitamin B I2 is quickly loses activity in an alkaline and very acidic environment, and destroyed under the influence of light and ultraviolet rays. Biological role. The biological value of vitamin B] 2 in the body is determined primarily by its powerful regulatory effect on blood formation processes. Absorbed vitamin B 12 is deposited in the liver, from where it enters the bone marrow as needed and regulates blood formation, activates the maturation of red blood cells. It also has a lipotropic effect, taking part in stimulating the synthesis of choline, enhances the processes of nucleic acid formation, improves using of protein by cells, accelerates the conversion of carotene to vitamin A, and stimulates wound healing processes. Cyanocobalamin deficiency. Vitamin В 12 deficiency in the body is the leading cause of disorder a function of hematopoiesis and anemia. Daily intake of vitamin Bi 2 in an adult is 2-5 pg. However, the body needs more of it when anemia and increased protein intake. Sources. Vitamin B l2 is found only in animal products. The lichest are the liver, kidneys, some dairy products, and egg yolk. Vitamin l2 in a small amount is synthesized by microorganisms of the colon. 253