Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.1 (tyrosinase)
 9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pigment of human substantia nigra, neuromelanin, has been thought to be derived from dopamine. To examine the genesis of neuromelanin, we advanced a new hypothesis that neuromelanin is formed by oxidation of dopamine and cysteinyldopamine. On the basis of this hypothesis, synthetic neuromelanins were obtained by tyrosinase oxidation of dopamine in the presence of various ratios of cysteine and were hydrolyzed with hydriodic acid to obtain 4-amino-3-hydroxyphenylethylamine (AHPEA). The AHPEA content in these synthetic melanins was shown to be proportional to the sulfur content. Eleven samples of human substantia nigra were treated as well and contents of AHPEA were found to be only trace amounts. These results suggest that cysteinyldopamine may not be incorporated into neuromelanin.
 ...
PMID:Cysteinyldopamine is not incorporated into neuromelanin. 179 80

Using model compounds of the melanic component of neuromelanin (NM) prepared by tyrosinase oxidation at various ratios of dopamine (DA) and cysteine (Cys) under physiological conditions, we examined a biosynthetic pathway to NM and its aging process by following the time course of oxidation to NM and the subsequent structural modification of NM under various heating conditions. Chemical degradation methods were applied to the synthetic NM. 4-Amino-3-hydroxyphenylethylamine (4-AHPEA) and thiazole-2,4,5-tricarboxylic acid (TTCA) were used as markers of benzothiazine and benzothiazole units, respectively. By following the time course of the biosynthetic pathway of synthetic NM, we found that neurotoxic molecules are trapped in NM. An aging simulation of synthetic NM showed that benzothiazine units in NM are gradually converted to benzothiazole during the aging process. Thus, natural NM was found to be similar to aged (heated) NM prepared from a 2:1 molar ratio of DA and Cys.
 ...
PMID:Biosynthetic pathway to neuromelanin and its aging process. 2293 12