Metabolic Consequences of Biotin Deficiency

The activities of biotin-dependent carboxylases fall in deficiency, resulting in impaired gluconeogenesis, with accumulation of lactate, pyruvate, and alanine, and impaired lipogenesis, with accumulation of acetyl CoA, resulting in ketosis. There are also changes in the fatty acid composition of membrane lipids. A variety of abnormal organic acids are excreted by both biotin-deficient patients and experimental animals (as shown in Table 11.1). There is accumulation of the apoenzymes of...

Human Pantothenic Acid Deficiency The Burning Foot Syndrome

In the 1940s, prisoners of war in the Far East who were severely malnourished showed, among other signs and symptoms of vitamin deficiency diseases, a new condition of paresthesia and severe pain in the feet and toes, which was called the burning foot syndrome or nutritional melalgia. Although it was tentatively attributed to pantothenic acid deficiency, no specific trials of pantothenic acid were conducted rather the subjects were given yeast extract and other rich sources of all vitamins as...

Photosynthesis of Cholecalciferol in the Skin

Cholecalciferol Synthesis

Cholecalciferol is formed nonenzymically in the skin by UV irradiation of 7-dehydrocholesterol, as shown in Figure 3.2. 7-Dehydrocholesterol is an HO v calciol (cholecalciferol) Figure 3.2. Synthesis of calciol from 7-dehydrocholesterol in the skin. intermediate in the synthesis of cholesterol that accumulates in the skin, but not other tissues. It is synthesized in the sebaceous glands, secreted onto the surface of the skin, and then absorbed into the epidermis. It is found throughout the...

The Role of Pyridoxal Phosphate in Steroid Hormone Action and Gene Expression

Steroid hormones act by binding to, and activating, nuclear receptors that then bind to hormone response elements on DNA, increasing (or sometimes decreasing) the transcription of specific genes. Early studies showed that pyridoxal phosphate reacts with a lysine residue in the steroid receptor protein and extracts the steroid-receptor complex from tight nuclear binding. The specificity for pyridoxal phosphate, but not pyridoxal, and the low physiological concentration at which the effect can be...