Structure and peroxidase activity of ferric Streptomyces clavuligerus orf10-encoded protein P450CLA: UV-visible, CD, MCD and EPR spectroscopic characterization

Abstract

O presente trabalho reporta a caracterização espectroscópica por absorção UV-visível, dicroísmo circular magnético (MCD) e ressonância paramagnética eletrônica (EPR) da proteína recombinante do tipo P450-canfora (P450CAM) codificada pela orf10 de Streptomyces clavuligerus (P450CLA) expressa por Escherichia coli Rosetta na forma nativa e associada a ligantes externos contendo os grupos β-lactamato, oxazol e derivado de alquilamina (álcool) do ácido clavulâmico. Considerando a diversidade de aplicações da enzima P450, sua reatividade com terc-butil-hidroperóxido (terc-BuOOH) foi caracterizada. O grupo heme da P450CLA apresenta-se covalentemente ligado e exibe características espectrais de UV-visível, CD e MCD de P450CAM, incluindo a banda Soret em 450 nm proveniente do complexo ferroso-CO. P450CLA foi convertido em espécies de valência alta pelo terc-BuOOH e promoveu cisão homolítica da ligação O−O. O perfil radicalar da reação foi terc-butiloxil como radical primário e metil e butilperoxil como radicais secundários. Os radicais metil e butilperoxil resultaram respectivamente da cisão-β do radical alcoxil e da reação do radical metil com oxigênio molecular.The present study reports the spectroscopic characterization by UV-visible absorption spectroscopy, magnetic circular dichroism (MCD) and electron paramagnetic resonance (EPR) of the recombinant orf10-encoded P450-camphor like protein (P450CLA) of Streptomyces clavuligerus expressed in Escherichia coli Rosetta in the native form and associated to external ligands containing the β-lactam, oxazole and alkylamine-derived (alcohol) moieties of the clavulamic acid. Considering the diversity of potential applications for the enzyme, the reactivity with tert-butylhydroperoxide (tert-BuOOH) was also characterized. P450CLA presents a covalently bound heme group and exhibited the UV-visible, CD and MCD spectral features of P450CAM including the fingerprint Soret band at 450 nm generated by the ferrous CO-complex. P450CLA was converted to high valence species by tert-BuOOH and promoted homolytic scission of the O−O bond. The radical profile of the reaction was tert-butyloxyl as primary and methyl and butylperoxyl as secondary radicals. The secondary methyl and butylperoxyl radicals resulted respectively from the β-scission of the alkoxyl radical and from the reaction of methyl radical with molecular oxygen.

Photodamage in a Mitochondrial Membrane Model Modulated by the Topology of Cationic and Anionic Meso‐Tetrakis Porphyrin Free Bases

“…). TMPyP (black line) and TPPS4 (gray line) exhibit, respectively, the intense Soret bands at 423 and 410 nm and the following lower intensity Q bands: Q y (0,0) at 518 and 516 nm, Q y (0,1) at 555 and 553 nm, Q x (0,0) at 586 and 584 nm and Q x (1,0) at 644 and 634 nm . Figure (right scale) shows that the emission spectrum of the white LED used for the electronic excitation of the porphyrins overlaps their Q bands.…”