Shin-ichi Nakayama

Spin-labeling study on the depth of the active site of papain

Abstract Papain is alkylated with a series of haloacetamide spin labels with varying distance between the haloacetamide residue and the nitroxide portion. The dependence of τ c on the distance and temperature revealed that the active site has a narrow neck and one auxiliary binding site around the neck. The depth of the active site is estimated about 10 A.

Study on the Interaction between Hemoglobin Izu (Macaca) and Organic Phosphates by Spin Labeling

ESR spectra of the carbonmonoxy, oxy, and deoxy derivatives of hemoglobin Izu [Hb Izu (Macaca): beta 83 (EF 7) Gly leads to Cys] labeled at cysteine beta 83 with maleimide spin label have been observed in the presence and absence of 2,3-diphosphoglycerate and inositol hexaphosphate. The tau c values obtained from the spectra indicated that inositol hexaphosphate binds to all the derivatives of Hb Izu, but 2,3-diphosphoglycerate only to the deoxy derivatives.

Spin-labeling of porcine pepsin and rhizopus chinensis acid protease by diazoketone reagents

Abstract The active site of porcine pepsin and that of rhizopus chinensis acid protease were labeled with diazoketone type spin labels, 4-(3-diazo-2-oxopropylidene)-2,2,6,6-tetramethylpiperidine-1-oxyl (I) and 3-(4-diazo-3-oxo- cis -1-butenyl)-2,2,5,5-tetramethylpyrroline-1-oxyl (II), respectively. The values of τ c showed that the nitroxide motion was only slightly restricted in the I bound enzymes. The trans isomer of II bound to another site of the enzymes. Addition of pepstatin reduced the nitroxide motion in all the labeled enzymes.