Fungal Strategies for Lignin Degradation - Botanical Research - page 272

enzymes present several structural similarities, both having two domains
with the heme sandwiched in between. MnP contains 10 major helices and
one minor helix as found in LiP. It presents a Mn(II)-binding site where Mn
coordinates to the carboxylate oxygens of Glu35, Glu39 and Asp179
( Fig. 3 A), the heme propionate oxygen and two water oxygens. Only one
of these residues is kept (Glu40) in LiP structure whereas the other two are
replaced by neutral residues (Ala36 and Asn182), resulting in the deletion of
the Mn(II)-binding site ( Fig. 3 B). MnPs have five instead of four disulfide
bonds compared to LiP, the additional bond being probably required to
stabilize the Mn(II)-binding site ( Wong, 2008 ).
Fig. 3. Comparison of active sites of MnP and LiP: (A) MnP (PDB 3M5Q ;
Sundaramoorthy et al., 1994 ) with the Glu35, Glu39 and Asp179 residues as well as
the Mn 2 þ ion; (B) LiP (PDB 1LG1 ; Poulos et al., 1993 ) with one of these residues kept
(Glu40) but the two others replaced by neutral residues (Ala36 and Asn182) resulting
in the disappearance of the Mn(II)-binding site.