Comparative analysis of catalases: spectral evidence against heme‐bound water for the solution enzymes

FEBS Letters

Simms, Melissa D.¹  Andersson, Laura A.¹  Willingham, Timothy R.¹  Johnson, Anna K.¹ 

[1] Department of Biochemistry, 103 Willard Hall, Kansas State University, Manhattan, KS 66502, USA

关键词: Catalase;    Distal heme pocket;    Magnetic circular dichroism (MCD) spectroscopy;    5-Coordinate vs. 6-coordinate heme systems;    Axial H2O-ligation;    MCD;    magnetic circular dichroism;    BL;    bovine liver;    ML;    Micrococcus luteus;    AN;    Aspergillus niger;    KPi;    potassium phosphate;    CD;    circular dichroism;    R z;    purity index A Soret/A 280;   

DOI  :  10.1016/0014-5793(95)00651-O

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

A recent X-ray structural analysis of M. luteus catalase indicates heme-bound H₂O trans to the proximal tyrosinate ligand, a finding in contrast to previous X-ray data reporting a 5-coordinate heme for bovine liver catalase. The presence of heme-bound H₂O, requiring displacement prior to substrate-binding, is likely to be catalytically significant for catalases. We have used magnetic circular dichroism (MCD) spectroscopy, a highly accurate method for assignment of heme spin- and coordination-states, to study native, solution forms of bovine liver, M. luteus, and A. niger catalases. All three enzymes display similar spectral features with the weak (∼5 Δϵ _m [moles·cm·Tesla]⁻¹ intensity typical of a 5-coordinate high-spin ferric heme. No evidence for H₂O-ligation, inducing a 6-coordinate heme, occurred upon variation of pH or buffer composition. Therefore, we suggest that the catalytically significant structure of catalases has an unoccupied heme binding site trans to the proximal tyrosinate heme ligand.

【 授权许可】

Unknown