Chapter 3. Thiamin, riboflavin, niacin, vitamin B6, pantothenic acid and biotin
Thiamin, riboflavin, niacin, vitamin B6, pantothenic acid and biotin . and the validity of the assessment of thiamin nutriture is improved with load test. .. its biochemical inter-relationship to riboflavin and vitamin B6, which are needed for the. or complete a reaction. These helpers include cofactors, coenzymes, and prosthetic groups, Many coenzymes are derived from vitamins. One class of these cofactors, termed coenzymes, consists of small organic Vitamins can be grouped according to whether they are soluble in water or in.
But first, let's review the idea that enzymes make reactions go faster. And they do this by lowering the activation energy peak of their respective reactions.
Let's also review the idea that enzymes bind their substrates at a location on the enzyme called the active site, which is where most of the reaction takes place. Now, not all enzymes are able to catalyze reactions on their own. And some need a little help. So if we have our enzyme here, trying to react with our substrate over here, sometimes something called a co-factor or a co-enzyme will be needed, which will also need to bind to the enzyme in order for it to function properly. And we're going to go over what co-enzymes and co-factors are and exactly how they work.
So first, we'll talk about what a co-enzyme is. Well, co-enzymes are organic carrier molecules. And what I mean by "organic" is that they're primarily carbon-based molecules.
And by "carrier," I mean that co-enzymes hold on to certain things for an enzyme to make the catalysis run a little more smoothly. And a great example of a co-enzyme is NADH, which acts as an electron carrier.
Vitamins Are Often Precursors to Coenzymes - Biochemistry - NCBI Bookshelf
Now if you remember the lactic acid fermentation reaction, where pyruvate is converted to lactic acid, you'd see that the enzyme catalyzing this reaction, lactate dehydrogenase, uses NADH as a co-enzyme in order to transfer electrons to the pyruvate molecule, in order to turn it into lactic acid. And in this sense, NADH is acting as an electron-carrying co-enzyme. Availability of vitamin B6 and pantothenate in an average American diet in man. The metabolism of small doses of vitamin B6 in men.
The influence of protein intake on vitamin B6 metabolism differs in young and elderly Humans. Assessment of vitamin B6 status. Studies on pregnant women and oral contraceptive users.
Oral contraceptives and vitamin B6. Pyridoxal phosphate and hypertensive disorders of pregnancy. Vitamin B6 Status and metabolism in pregnancy. Vitamin B6 metabolism and role in growth. Influence of vitamin B6 intake on the content of the vitamin in Human milk. Dietary intake of total and glycosylated vitamin B6 and the vitamin B6 nutritional status of unsupplemented lactating women and their infants.
Vitamin B6 status during childhood: Vitamin B6 requirements of men. Human Vitamin B6 Requirements Proceedings of a workshop. The effect of dietary protein on the metabolism of vitamin B6 in Humans. Urinary 4-pyridoxic acid, plasma pyridoxal phosphate, and erythrocyte aminotransferase levels in oral contraceptive users receiving controlled intakes of vitamin B6. Vitamin B6 requirement and status assessment: Vitamin B6 status of women with a constant intake of vitamin B6 changes with three levels of dietary protein.
Changes in vitamin B6 status indicators of women fed a constant protein diet with varying levels of vitamin B Vitamin B6 requirements of elderly men and women.
Co-factors, co-enzymes, and vitamins
Vitamin status and intake as primary determinants of homo-cysteinemia in an elderly population. Maternal and foetal plasma levels of pyridoxal phosphate at term: Adequacy of vitamin B6 supplementation during pregnancy: Vitamin B6 in infancy: Pantothenic acid and co-enzyme A. Metabolic response to a pantothenic acid deficient diet in Humans. Pantothenic acid status of adolescents.
Natural Vitamins and Coenzyme Forms
Enzymes for liberation of pantothenic acid in blood: Water-soluble vitamins in Human milk. Handbook of Milk Composition. Human milk intake and growth in exclusively breast-fed infants. Studies in Human lactation: Energy and protein intakes of breast-fed and formula-fed infants during the first year of life an their association with growth velocity: Pantothenic acid status of free living adolescent and young adults.
Pantothenic acid nutritional status in the elderly-institutionalized and noninstitutionalized. Pantothenic acid and vitamin E in the British household food supply. Pantothenic acid status of pregnant and lactating women. Present Knowledge in Nutrition, 7th edition. Increased urinary excretion of 3-hydroxyisovaleric acid and decreased urinary excretion of biotin are sensitive early indicators of decreased status in experimental biotin deficiency.
The metabolism of biotin and analogues. Present Knowledge in Nutrition, 4th edition. The Nutrition Foundation, p. Identification of biotin sulfone, bisnorbiotin methylketone, and tetranorbiotin-l-sulfoxide in Human urine. Biotin-responsive in vivo carboxylase deficiency in two siblings with secretory diarrhea receiving total parenteral nutrition.
Biotin deficiency in a child on long-term TPN. Biotin deficiency complicating parenteral alimentation: Vitamin A retinol is the precursor of retinal, the light-sensitive group in rhodopsin and other visual pigments Section A deficiency of this vitamin leads to night blindness.
In addition, young animals require vitamin A for growth. Retinoic acid, which contains a terminal carboxylate in place of the alcohol terminus of retinol, serves as a signal molecule and activates the transcription of specific genes that mediate growth and development Section A metabolite of vitamin D is a hormone that regulates the metabolism of calcium and phosphorus.
A deficiency in vitamin D impairs bone formation in growing animals. This vitamin reacts with and neutralizes reactive oxygen species such as hydroxyl, radicals before they can oxidize unsaturated membrane lipids, damaging cell structures.