Noriko Mohri

Strain- and organ-dependent differences in induction of aryl hydrocarbon hydroxylase activity by 3-methylcholanthrene

Several polyaromatic hydrocarbons are suspected to be carcinogenic and may be a major cause of the human lung cancer. In the murine tissues, liver, lung, kidney, small intestine, lymphocytes etc., the first step of the metabolism of polyaromatic hydrocarbons involves the enzyme aryl hydrocarbon hydroxylase (AHH), which is known as a component of the microsomal mixed function oxidase system dependent on NADPH and cytochrome P-450 (P-450). Hepatic and extrahepatic AHH is induced by polyaromatic hydrocarbons such as 3-methylcholanthrene (MC) and the inducibility is under the control of the aromatic hydrocarbon (Ah) locus; certain inbred strains of mice are susceptible of AHH induction by MC treatment (Ah responsive strains), while other inbred strains are not (Ah non-responsive strains). The objective of this study is to understand more fully strain- and organ-dependent differences in inducibility of AHH by MC with the genetically established mouse strains as materials. Also the AHH levels of blood lymphocytes and splenic lymphocytes are compared with those of several freshly excised organs of the strains of mice.

Proton NMR resonance assignments and surface accessibility of tryptophan residues of a dimeric phospholipase A2 from Trimeresurus flavoviridis

Proton NMR spectra of a dimeric phospholipase A2 from Trimeresurus flavoviridis have been recorded. N‐1 proton resonances of the tryptophan indole rings have been detected and assigned to specific positions, Trp‐3/Trp‐30, Trp‐68 and Trp‐108, by comparing the spectra of the enzyme derivatives with tryptophans oxidized to differing extents. Photo‐CIDNP experiments have revealed that Trp‐68 and Trp‐108 are exposed while Trp‐3 and Trp‐30 are buried in the molecule. This is consistent with the X‐ray crystal structure of a homologous phospholipase A2 from Crotalus atrox where residues 3 and 30 are located at a dimer interface, but inconsistent with the results of stepwise oxidation of tryptophan residues.