Coordination modes of tyrosinate-ligated catalase-type heme enzymes: Magnetic circular dichroism studies of Plexaura homomalla allene oxide synthase, Mycobacterium avium ssp. paratuberculosis protein-2744c, and bovine liver catalase in their ferric and ferrous states

Abstract

Bovine liver catalase (BLC), catalase-related allene oxide synthase (cAOS) from Plexaura homomalla, and a recently isolated protein from the cattle pathogen Mycobacterium avium ssp. paratuberculosis (MAP-2744c (MAP)) are all tyrosinate-ligated heme enzymes whose crystal structures have been reported. cAOS and MAP have low (< 20%) sequence similarity to, and significantly different catalytic functions from, BLC. cAOS transforms 8R-hydroperoxy-eicosatetraenoic acid to an allene epoxide, whereas the MAP protein is an organic peroxide-dependent peroxidase. To shed light on the functional differences among these three proteins, we have investigated the heme iron coordination properties of these tyrosinate-ligated heme proteins in their ferric and ferrous states using magnetic circular dichroism and UV-visible absorption spectroscopy. The MAP protein shows remarkable spectral similarities to cAOS and BLC in its native Fe(III) state, but clear differences from ferric His93Tyr Mb, which may be attributed to the presence of an Arg+-Nω-H … O-Tyr (proximal heme axial ligand) hydrogen bond in the first three heme proteins. Furthermore, the spectra of Fe(III)-CN−, Fe(III)-NO, Fe(II)-NO (except for five-coordinate MAP), Fe(II)-CO, and Fe(II)-O2 states of cAOS and MAP, but not H93Y Mb, are also similar to the corresponding six-coordinate complexes of BLC, suggesting that a tyrosinate (Tyr-O−) is the heme axial ligand trans to the bound ligands in these complexes. The Arg+-Nω-H to −O-Tyr hydrogen bond would be expected to modulate the donor properties of the proximal tyrosinate oxyanion and, combined with the subtle differences in the catalytic site structures, affect the activities of cAOS, MAP and BLC.

A Catalase-related Hemoprotein in Coral Is Specialized for Synthesis of Short-chain Aldehydes

“…1). The absorbance shifted to 427 nm in the CO complex of the dithionite-reduced (ferrous) enzyme, a value close to the reported lambda max of the P. homomalla CO complex of ferrous-cAOS (427 nm) (18,19).…”

Sulfheme formation during homocysteine S-oxygenation by catalase in cancers and neurodegenerative diseases

“…Its exposure to CO generates a new species ( λ max =412 and 626 nm) with spectral properties that differ from the classical 6-coordinate CAT–Fe(II)-CO ( λ max =425, 544 and 570 nm) species but are fairly analogous to the one ascribed to carboxyferrosulfcatalase (α-band at 627 nm; Fig. 2d)2431. These observations suggest that the second species corresponds to an unusually stable Fe(II) sulfcatalase-like species.…”

“…This Fe(II) species displays α-bands at 591, 636 and 658 nm and shares some spectral similarities with CAT–Fe(II) (α-bands at 561 and 595 nm) or ferrosulfcatalase (α-band at 635 nm; Fig. 2b)2431. Its exposure to CO generates a new species ( λ max =412 and 626 nm) with spectral properties that differ from the classical 6-coordinate CAT–Fe(II)-CO ( λ max =425, 544 and 570 nm) species but are fairly analogous to the one ascribed to carboxyferrosulfcatalase (α-band at 627 nm; Fig.…”

Heme Binding by Corynebacterium diphtheriae HmuT: Function and Heme Environment

“…The H136A mutant was compared with three tyrosine models: ShuT (26), BLC (72–74), and Mb-H93Y (75) (Figure S8). In the UV-visible spectra, the Soret peaks for all four proteins were similar, with maxima located from 400 to 407 nm.…”