Perossidasi

The active site of peroxidases and the residues conserved in the different peroxidases.

HRP = horseradish peroxidase (representative of plant peroxidases)
CcP = cytochrome c peroxidase (from Baker's yeast)
LiP = lignin peroxidase (from the fungus Phanerochaete chrysosporium)
MnP = manganese peroxidase (from the fungus Phanerochaete chrysosporium)

The catalytic cycle of peroxidases

Differences between

Myoglobin and Peroxidases

Myoglobin Peroxidases

Fe(II)-heme Fe(III)-heme

Fe³⁺/Fe²⁺ +160mV Fe³⁺/Fe²⁺ -300/100mV

proximal site: weak proximal site: strong

H-bond between H-bond between

proximal His and a peptidic CO proximal His and the carboxylic group of a proximal Asp

distal site: more distal site: more

hydrophobic hydrophylic

The heme site in myoglobin and peroxidases

Redox Potential for Fe³⁺/Fe²⁺

1.) HRP	- 278 mV
2.) CcP	- 194 mV
3.) LiP	- 142 mV
4.) MnP	- 93 mV

Redox Potential for Compound I
and Compound II

.	Compound I	Compound II
1.) HRP	0.898V	0.869V
2.) CcP	0.740V	.
3.) LiP	1.4 V	.
4.)MnP	1.5 V	.

Peroxidases from different origin have different substrates

The substrate of lignin peroxidase (LiP) is a high molecular weight polymer

Schematic structural formula for Lignin

( molecular weight 600,000-1,000,000)

Spectroscopic properties of the Peroxidases

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Myoglobin	Peroxidases
Fe(II)-heme	Fe(III)-heme
Fe³⁺/Fe²⁺ +160mV	Fe³⁺/Fe²⁺ -300/100mV
proximal site: weak	proximal site: strong
H-bond between	H-bond between
proximal His and a peptidic CO	proximal His and the carboxylic group of a proximal Asp
distal site: more	distal site: more
hydrophobic	hydrophylic