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Models for the Active Center of Pterin‐Containing Molybdenum Enzymes: Crystal structure of a molybdenum complex with sulfur and pterin ligands
Author(s) -
Fischer Berthold,
Schmalle Helmut W.,
Baumgartner Markus R.,
Viscontini Max
Publication year - 1997
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19970800110
Subject(s) - pterin , chemistry , molybdenum , ligand (biochemistry) , protonation , stereochemistry , monoclinic crystal system , molybdenum cofactor , crystallography , crystal structure , active site , pyridine , cofactor , inorganic chemistry , enzyme , medicinal chemistry , organic chemistry , ion , biochemistry , receptor
The first crystal structure of a molybdenum complex 9 with a hydrogenated pterin and a sulfur ligand contributes to the discussion about the active center of molybdenum and tungsten enzymes containing a molybdopterin cofactor. Complex 9 was synthesized through a redox reaction of [Mo VI O 2 (LN‐S 2 )] ( 8 ; LN‐S 2 = pyridine‐2, 6‐bis(methanethiolato)) with 5, 6, 7, 8‐tetrahydropterin ( 7 ). 2 HCl (H 4 Ptr.2 HCl). The complex crystallizes, with a non‐coordinating Cl‐atom acting as a counterion, in the monoclinic space group C2/c (No. 15) with cell dimensions a = 22.900(5), b = 10.716(2), c = 17.551(4) Å, β = 120.36(3)°, and Z = 8. We interpret 9 as [Mo IV O(LN‐S 2 )(H + ‐q‐H 2 Ptr)]Cl (q = quinonoid; H 2 Ptr = dihydropterin), i.e., a Mo IV monooxo center coordinated by a pyridine‐2, 6‐bis(methanethiolato) ligand and a protonated dihydropterin. The spectroscopic properties of this new complex are comparable to those of other crystalline molybdenum complexes of hydrogenated pterins without additional S‐coordination. The slightly H 2 O‐soluble complex 9 reacts with the natural enzyme substrate DMSO very slowly, possibly due to the lack of easily dissociable ligands at the metal center.