STUDIES OF METALLOBLEOMYCINS BY ELECTRONIC SPECTROSCOPY, ELECTRON-SPIN RESONANCE SPECTROSCOPY, AND POTENTIOMETRIC TITRATION

被引:73
作者
SUGIURA, Y
ISHIZU, K
MIYOSHI, K
机构
[1] EHIME UNIV, DEPT CHEM, MATSUYAMA, EHIME 790, JAPAN
[2] NIIHAMA TECH COLL, NIIHAMA, EHIME 792, JAPAN
关键词
D O I
10.7164/antibiotics.32.453
中图分类号
Q81 [生物工程学(生物技术)]; Q93 [微生物学];
学科分类号
071005 ; 0836 ; 090102 ; 100705 ;
摘要
The 1: 1 bleomycin-A2-Cu(II) complex shows an absorption maximum at 595 nm (ε 120), circular dichroism extrema at 555 nm (Δε+1.21) and 665 nm (—0.61), and electron spin resonance (ESR) signal with g||,=2.211, g⊥=2.055, and A|| =178 χ10-4 cm-1. The formation constant (log K = 12.630) and deprotonation constant (pKc = 3.585) of the 1: 1 bleomycin-Cu(II) complex were determined by computer analysis of potentiometric data. The results of potentiometric titration also indicate that the stability of bleomycin-metal complexes is in the order Fe(II) < Co(II) < Ni(II) < Cu(II) > Zn(II) and that these divalent metal complexes have a similar coordination environment. The bleomycin-Cu(II) complex has substantially a square-pyramidal configuration in which the secondary amine nitrogen, pyrimidine(N-1) ring nitrogen, deprotonated peptide nitrogen of histidine residue, and histidine imidazole(N-1) nitrogen coordinate to Cu(II) as planar ligand donors, and the α-amino nitrogen as axial donor. The specific Cu(II)-binding site of bleomycin has been compared with that of human serum albumin. © 1979, JAPAN ANTIBIOTICS RESEARCH ASSOCIATION. All rights reserved.
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页码:453 / 461
页数:9
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