Homeostasis of Dopamine
Nira Ben-Jonathan in Dopamine, 2020
TH is a mixed function oxidase that uses L-tyrosine and molecular oxygen as substrates, and L-tetrahydrobiopterin (BH4) and ferrous iron (Fe2+) as cofactors [3]. Tyrosine is one of the 20 standard amino acids used by cells to synthesize proteins. It is a nonessential amino acid with a polar side chain group. Given its natural abundance, catecholamine levels are not influenced either by changing the dietary levels of tyrosine or by its parenteral administration, even at large amounts. Because of its essential role as a cofactor in TH enzymatic activity, a deficiency in BH4 can cause systemic deficiencies of catecholamines. One example of BH4 deficiency is the development of dopamine-responsive dystonia, characterized by increased muscle tone and Parkinsonian features. This condition can be treated with carbidopa/levodopa which directly restores dopamine levels within the brain.
Tyrosine
Linda M. Castell, Samantha J. Stear (Nottingham), Louise M. Burke in Nutritional Supplements in Sport, Exercise and Health, 2015
A series of pre-clinical animal studies clearly indicate that tyrosine reduces many of the adverse effects of acute stress on cognitive performance in a wide variety of stressful environments. Although it has been difficult to demonstrate conclusively that tyrosine has beneficial effects in humans, in part due to ethical concerns, most of the evidence suggests that tyrosine is useful as an acute treatment to prevent stress-related declines in cognitive function. After finding that tyrosine supplementation promoted working memory updating, specifically in the demanding but not the easier condition of the N-back task (subjects were required to decide whether each stimulus in a sequence matched the one that appeared ‘n’ items ago), Colzato et al. (2013) suggested that tyrosine selectively targets cognitive control operations. This further suggests that tyrosine can replete cognitive resources when more control is needed. Tyrosine affects the same neurotransmitter systems as the amphetamines and related drugs, which are potent performance-enhancing compounds, although they have many side effects (Yeghiayan et al., 2001).
The Importance of Personalized Nutrition in Psychological Disorders
Nilanjana Maulik in Personalized Nutrition as Medical Therapy for High-Risk Diseases, 2020
Catecholamines (norepinephrine, dopamine and epinephrine) are synthesized from tyrosine by neurons in the brain. Being one of the essential amino acids, L-phenylalanine is the direct precursor of tyrosine; however, the body receives the two through a normal diet. After being formed by tyrosine, dihydroxyphenylalanine (DOPA) is transformed into dopamine, which in return forms norepinephrine and then epinephrine. Neurotransmitters norepinephrine and dopamine are involved in depression. Few studies have investigated whether there is a relationship between tyrosine deficiency and depression (Parker and Brotchie 2011). Nevertheless, plasma concentrations of tryptophan, tyrosine and phenylalanine levels are observed to be lower among individuals with ADHD (Bornstein, Baker et al. 1990).
Metabolomic assessment of mechanisms underlying anti-renal fibrosis properties of petroleum ether extract from Amygdalus mongolica
Published in Pharmaceutical Biology, 2021
Chen Gao, Wan-fu Bai, Hong-bing Zhou, Hai-mei Hao, Ying-chun Bai, Quan-li Liu, Hong Chang, Song-li Shi
l-Tyrosine is a non-essential amino acid and a precursor of various bioactive molecules, including brain catecholamine neurotransmitters including norepinephrine and dopamine (DA) (Wang et al. 2019). DA is an endogenous nitrogen-containing organic compound that is the intermediate product of l-tyrosine biosynthesis from dihydroxyphenylalanine. Gülçin (2007) showed that l-tyrosine scavenged free radicals like DPPH (1,1-diphenyl-2-picrylhydrazyl radical), ABTS, superoxide anion and H2O2, and also reduced ferrous ion chelation. Øvrehus et al. (2019) found that 11 amino acids, including tyrosine, phenylalanine, dopamine, homocysteine and serine, were affected in hypertensive nephrosclerosis patients. This disorder is characterised by a 30–70% decrease in urine output, endothelial dysfunction, atherosclerosis and renal fibrosis due to dysregulated dopamine biosynthesis in the kidney (Zhang 2013).
Distortion product otoacoustic emission sensitivity to different solvents in a population of industrial painters
Published in International Journal of Audiology, 2020
Renata Sisto, Luigi Cerini, Filippo Sanjust, Damiano Carbonari, Monica Gherardi, Andrea Gordiani, Nunziata L’Episcopo, Enrico Paci, Daniela Pigini, Giovanna Tranfo, Arturo Moleti
The oxidative stress and the nitrosative stress are recognised to cause many acute and chronic diseases and even of the physiological aging process. The oxidation process involve DNA, RNA, lipids and proteins. In the proteins usually this process implies the introduction of functional groups that could alter the protein function and metabolism. The tyrosine is an amino acid present in the most part of the proteins. This amino acid is slightly hydrophilic due to the aromatic benzene ring that transport a hydroxyl group. One of the most important biomarker of the protein oxidation is the 3 Nitrotyrosine (3NO2tyrosine), an oxidation product of the tyrosine, that is produced in the reaction of NO or of the NO3 and that represents a damage on proteins and amino acids (Bandookwala et al. 2019). In this paper, the concentration of tyrosine and of its oxidation product 3NO2tyrosine were measured and compared at the beginning and the end of the work-shift. The methylation product of the cytidine, 5-methylcytidine, was also quantified as a measure of the damage to the RNA. The 5-methylcytidine is one of the epigenetic marks of DNA and RNA, and aberrant levels of this modified nucleoside were found to be associated with various cancers (Guo et al. 2018).
Predictive serum biomarkers of patients with cerebral infarction
Published in Neurological Research, 2022
Yan Kong, Yu-qing Feng, Ya-ting Lu, Shi-sui Feng, Zheng Huang, Qian-yi Wang, Hui-min Huang, Xue Ling, Zhi-heng Su, Yue Guo
During phenylalanine, tyrosine, and tryptophan biosynthesis, phenylalanine is initially converted into tyrosine in vivo. It has been reported that the increase in phenylalanine in the blood significantly increases abnormalities in electroencephalogram and the occurrence of cerebral ischemia in varying degrees. Moreover, high phenylalanine content can variably aggravate cerebral ischemia and brain damage in children [18–22]. In our study, the content of tyrosine was significantly higher in the patient group than that of the control group. We speculate that this is attributed to the increased content of phenylalanine, which is easily converted into tyrosine and thus, increasing the content of tyrosine. Taken together, the increased serum tyrosine level and the dysfunction of phenylalanine, tyrosine, and tryptophan biosynthesis in cerebral infarction patients may be a cause of cerebral infarction. Moreover, we suggest that treatment of cerebral infarction should aim to reduce phenylalanine.
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