Factors affecting hydrogen-tunneling contribution in hydroxylation reactions promoted by oxoiron(IV) porphyrin π-cation radical complexes.

Hydrogen atom transfer with a tunneling effect (H-tunneling) has been proposed to be involved in aliphatic hydroxylation reactions catalyzed by cytochrome P450 and synthetic heme complexes as a result of the observation of large hydrogen/deuterium kinetic isotope effects (KIEs). In the present work, we investigate the factors controlling the H-tunneling contribution to the H-transfer process in hydroxylation reaction by examining the kinetics of hydroxylation reactions at the benzylic positions of xanthene and 1,2,3,4-tetrahydronaphthalene by oxoiron(IV) 5,10,15,20-tetramesitylporphyrin π-cation radical complexes ((TMP(+•))Fe(IV)O(L)) under single-turnover conditions. The Arrhenius plots for these hydroxylation reactions of H-isotopomers have upwardly concave profiles.

Molecular characteristics of a single and novel form of carp (Cyprinus carpio) monoamine oxidase.

Two mammalian monoamine oxidases (MAO), MAO-A and MAO-B, are similar in primary structures but have unique substrate/inhibitor selectivities. Carp (Cyprinus carpio) contains a MAO enzyme (C-MAO) with properties different from MAO-A and MAO-B. To determine the molecular characteristics of C-MAO and its phylogenetic relationship with other fish and mammalian MAOs, the primary structure of C-MAO was estimated.

Absence of tissue-bound semicarbazide-sensitive amine oxidase activity in carp tissues.

We have previously reported that carp (Cyprinus carpio) tissue mitochondria contain a novel form of monoamine oxidase (MAO), which belongs neither to MAO-A nor to MAO-B of the mammalian enzyme. This conclusion results from the findings that the carp MAO was equally sensitive to a selective MAO-A inhibitor clorgyline and to the MAO-B selective inhibitor l-deprenyl, when tyramine, a substrate for both forms, serotonin or beta-phenylethylamine, a substrate for either A or B-form of mammalian MAO, was used. In the present study, we tried to detect another amine oxidase, termed tissue-bound semicarbazide-sensitive amine oxidase (SSAO), activity in carp tissues.

Nucleotide sequences of putative cDNAs for guinea-pig monoamine oxidase.

To study the molecular structure of guinea pig monoamine oxidase (MAO) and its phylogenetic relationship with other mammalian MAOs, we determined nucleotide sequences of putative MAO cDNAs isolated from guinea pig tissues. Both the 5'- and 3'-ends of the cDNAs were amplified using the RACE (rapid amplification of cDNA ends) method. The sequence (1924 bp) of a putative guinea-pig MAO-B cDNA covers a complete coding region that corresponds to 521 amino acids.