Detail of "29539-03-5"

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Chemical intermediates in dopamine oxidation by tyrosinase, and kinetic studies of the process

Chemical intermediates in dopamine oxidation by tyrosinase, and kinetic studies of the process. Jimenez, M.; Garcia-Carmona, F.; Garcia-Canovas, F.; Iborra, J. L.; Lozano, J. A.; Martinez, F. (Dep. Bioquim., Univ. Murcia, Murcia, Spain). Arch. Biochem. Biophys., 235(2), 438-48 (English) 1984. CODEN: ABBIA4. ISSN: 0003-9861. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) A minor pathway for dopamine [51-61-6] oxidn. to dopaminochrome [39984-17-3] by tyrosinase [9002-10-2], is proposed. Characterization of intermediates in this oxidative reaction and stoichiometric detn. were undertaken. After oxidizing dopamine with mushroom tyrosinase or NaIO4 in a pH range of 6.0-7.0, it was spectrophotometrically possible to detect O-dopaminoquinone-H+ [84279-61-8] as the 1st intermediate in this pathway. The steps for dopamine transformation to dopaminochrome are as follows: dopamine ? O-dopaminoquinone-H+ ? O-dopaminequinone [50673-96-6] ? leukodopaminochrome [29539-03-5] ? dopaminochrome. No participation of O was detected in the conversion of leukodopaminochrome to dopaminochrome. Scanning spectroscopy and graphical anal. of the obtained spectra also verified that dopaminequinone-H+ was transformed into aminochrome in a const. ratio. The stoichiometry equation for this conversion is 2 O-dopaminequinone-H+ ? dopamine + dopaminochrome. The pathway for dopamine oxidn. to dopaminochrome by tyrosinase has been studied as a system of various chem. reactions coupled to an enzymic reaction. A theor. and exptl. kinetic approach is proposed for such a system; this type of mechanism has been named Enzymic-chem.-chem. (EZCC). Rate consts. for the implied chem. steps at different pH and temp. values were evaluated from the measurement of the lag period arising from the accumulation of dopaminochrome that took place when dopamine was oxidized at acid pH. The thermodn. activation parameters of the chem. steps, the deprotonation of dopaminequinone-H+ to dopaminequinone, and the internal cyclization of dopaminequinone to leukodopaminochrome were calcd.

Kinetics and mechanism of oxidation paths of some catecholamines with periodic acid

Kinetics and mechanism of oxidation paths of some catecholamines with periodic acid. Pelizzetti, Ezio; Mentasti, Edoardo; Pramauro, Edmondo (Ist. Chim. Anal., Univ. Torino, Turin, Italy). J. Chem. Soc., Perkin Trans. 2, (14), 1651-5 (English) 1976. CODEN: JCPKBH. DOCUMENT TYPE: Journal CA Section: 22 (Physical Organic Chemistry) The kinetics and mechanism of oxidn. of adrenalin (I), L-dopa (II), and dopamine (III) to the corresponding open-chain o-benzoquinones with periodic acid were investigated at pH 0-7, at different temps. The reactions were first-order in each reagent and were strongly pH-dependent which was explained in terms of differently protonated reagent couples. At pH>4 the substituted o-benzoquinones rearranged with cyclization of the side chain to give the corresoponding 5,6-dihydroxy-2,3-dihydroindoles which were then rapidly oxidized to 2,3-dihydroindole-5,6-quinones.There are some commonly used reagents with their cas registry numbers 29539-03-5 and 59-92-7 in this article. The rates of cyclization decreased significantly in the order I .mchgt. II > III. .