Yasuyuki Ogura

Mössbauer effect in bacterial catalase

Abstract The Mossbauer spectra in native catalase (EC 1.11.1.6) prepared from 57Fe-enriched bacteria have been measured from 2.1 to 195 °K. At low temperature the spectra consist of a quadrupole doublet of 0.9 mm/s and a broad magnetic hyperfine pattern. By applying a small magnetic field, the magnetic pattern exhibits six well-defined lines with an effective field of 293 kG and a quadrupole perturbation of (−)0.45 mm/s, while the quadrupole doublet is not influenced. At high temperatures the magnetic subspectrum collapses. The area of the two subspectra are equal within experimental error over a wide temperature range. These results suggest that the four hematins in bacterial catalase show pair-wise different interactions, probably due to different Fe-Fe interatomic distances. Both subspectra are very similar to those of crystalline hemin and dilute hemin, and they are characterized by a ferric high-spin state. This is in agreement with the results of EPR, magnetic susceptibility and optical absorption measurements.

Kinetic studies of the old yellow enzyme. I. The reaction mechanism of the enzyme with reduced nicotinamide adenine dinucleotide.

The reaction mechanism of old yellow enzyme (NADPH:(acceptor) oxidoreductase, EC 1.6.99.1) was kinetically investigated using NADH as substrate. The enzyme was reduced by NADH via a reaction intermediate which has a specific absorption spectrum. This intermediate decomposed to yield a reduced enzyme and NAD+ through an inrreversible first-order reaction step. The reduced enzyme was reoxidized by oxygen through a second-order reaction process. Individual values of elementary rate constants were measured and a computer simulation of the reaction process was carried out. No involvement of free radical of flavin semiquinone in the reaction process could be shown.