The enzyme is involved in the last step of producing tetrahydrobiopterin, better known as BH4. BH4 is involved in the processing of amino acids and the production of neurotransmitters, specifically that of dopamine and serotonin which are primarily used in transmission of signals between nerve cells in the brain. The mutation in the SPR gene interferes with the production of the enzyme by producing enzymes with little or no function at all. This interference results in a lack of BH4 specifically in the brain. The lack of BH4 only occurs in the brain because other parts of the body adapt and utilize alternate pathways for the production of BH4. The mutation in the SPR gene leads to nonfunctional sepiapterin reductase enzymes, which results in a lack of BH4 and ultimately disrupts the production of dopamine and serotonin in the brain. The disruption of dopamine and serotonin production leads to the visible symptoms present in patients suffering from sepiapterin reductase deficiency. SR deficiency is considered an inherited autosomal recessive condition disorder because each parent carries one copy of the mutated gene, but typically do not show any signs or symptoms of the condition. Diagnosis
CSF neurotransmitter screening
The diagnosis of SR deficiency is based on the analysis of the pterins and biogenic amines found in the cerebrospinal fluid (CSF) of the brain. The pterin compound functions as a cofactor in enzyme catalysis and biogenic amines which include adrenaline, dopamine, and serotonin have functions that vary from the control of homeostasis to the management of cognitive tasks.
Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heat loss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat. Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss. Loss of this function contributes to the massive fluid loss in burns. Aesthetics and communication: others see our skin and can assess our mood, physical state and attractiveness. Storage and synthesis: acts as a storage centre for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin. Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation. Absorption: the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is negligible". In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in many other organisms. Water resistance: The skin acts as a water-resistant barrier so essential nutrients are not washed out of the body. Skin flora
The human skin is a rich environment for microbes. Around 1000 species of bacteria from 19 bacterial phyla have been found.