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Occurrence and structure
Thiamine is found in both plant and animal products. Its chemical structure is characterized by a pyrimidine ring (containing two nitrogen (N) atoms in its six-membered ring) and a thiazole ring (containing one sulfur (S) atom in its five-membered ring). Occurrence:
- Vegetable: (wheat germ, sunflower seeds, soybeans)
Thiamine must first be activated in order to fulfill its functions in the body.
This is done by attaching two phosphate residues (pyrophosphate), which are coupled to each other, as these two are connected by a high-energy bond. In this activated form, thiamine is an auxiliary factor (cofactor) in reactions of digression to these metabolic pathways: The pyruvate dehydrogenase reaction follows glycolysis (conversion of the sugar glucose into pyruvate with – however, lower – energy yield) and converts the pyruvate formed there into acetyl-CoA, which is then introduced into the citrate cycle. This reaction only takes place if enough oxygen is available, i.e. it is aerobic.
- Citrate cycle (here it serves as a helper for the enzyme alpha-ketoglutarate dehydrogenase)
- Pyruvate conversion to acetyl-CoA (helper of pyruvate dehydrogenase)
- Pentose phosphate pathway (helper of transketolase)
The subsequent citrate cycle (citric acid cycle or tricarboxylic acid cycle) also only takes place under aerobic conditions and serves to provide so-called reduction equivalents. These can be converted in the subsequent respiratory chain into energy in the form of ATP (adenosine triphosphate, which is the energy currency of the body). In the citrate cycle, acetyl-CoA is broken down to carbon dioxide with the formation of these reduction equivalents and the production of two energy-rich compounds (GTP – guanosine triphosphate, so to speak a brother of ATP).
The pentose phosphate pathway serves primarily to provide NADPH reduced nicotinamide adenine dinucleotide phosphate), which is essential for protection against oxygen radicals that can cause great damage in the organism. The deficiency disease resulting from thiamine deficiency is called BeriBeri and is hardly found in industrialized countries today. However, it is still found in countries where mainly polished rice is consumed, which does not contain any thiamine. Symptoms are skeletal muscle atrophy, heart function disorders and water retention (edema). Water-soluble (hydrophilic) vitamins: Fat-soluble (hydrophobic) vitamins:
- Vitamin B1 – thiamine
- Vitamin B2 – Riboflavin
- Vitamin B3 – Niacin
- Vitamin B5 – pantothenic acid
- Vitamin B6 – PyridoxalPyridoxinPyridoxamine
- Vitamin B7 – biotin
- Vitamin B9 – folic acid
- Vitamin B12 – cobalamin
- Vitamin A – Retinol
- Vitamin C – Ascorbic acid
- Vitamin D – Calcitriol
- Vitamin E – tocopherol
- Vitamin K – PhylloquinoneMenachinone
