2-His-l-carboxylate triad

In our quest to find suitable N,N,0- igands as models for the active sites of the facial 2-His-l-carboxylate triad in iron and zinc containing enzymes, heteroscorpionate ligands like bis(3,5-dimethylpyrazol-... 

Hegg, E. L. and L. Que (1997). The 2-His-l-carboxylate facial triad-An emerging structural motif in mononuclear non-heme iron(II) enzymes. Eur. J. Biochem. 250(3) 625-629. 

Figure 13.19 Reactions catalysed by each of the five families of mononuclear non-haem iron enzymes with a 2-His-l-carboxylate facial triad. Dioxygen is labelled to indicate the fate of each oxygen atom. (From Koehntop et al., 2005. With kind permission of Springer Science and Business Media.)...

The 2-His-l-Carboxylate Facial Triad in Non-Heme Iron Oxygenases 101... 

The number of known or presumed mononuclear, non-heme iron oxygenases and related enzymes continues to grow. This is due to intensive biochemical research and especially based on sequence data derived from genome research projects i.14). For several of these enzymes structural data are available by now from protein crystallography (12-14). In many of the iron oxygenases the iron is facially bound by two histidines and one carboxylate donor, either glutamic acid or aspartic acid. Thus, the term 2-His-l-carboxylate facial triad has been introduced by L. Que Jr. for this motif (19). 

His-l-carboxylate facial triad. In these ligands the two pyrazol-l-yl... 

Inspired by the 2-His-l-carboxylate facial triad our interest focused on the development of a new facially coordinating tripod ligand which... 

Scheme 2.5 Ligands used to synthesize structural and/or functional models for iron enzymes containing a 2-His-l-carboxylate facial triad (a) R3TACN (TACN = 1,4,7-triazacyclononane) [25] (b) TpR,R [differently substituted hydridotris(pyrazol-l-yl)borates] [27] (c) differently substituted bis(pyrazol-l-yl)acetates [29] (d) differently substituted 3,3-bis(1 -alkylimidazol-2-yl)propionates [30],...

Crystal structures for a number of enzymes in this family are now available. Despite the fact that many of these enzymes exhibit minimal sequence identity, they have a conserved Hx(D/E)x H sequence that provides the three endogenous protein ligands of the recurring 2-His-l-carboxylate facial triad motif that binds the high-spin iron(n) center. Three solvent molecules on the opposite face complete the iron coordination sphere. 

K. D. Koehntop, J. P. Emerson, L. Que, Jr., The 2-His-l-carboxylate facial triad A versatile platform for dioxygen activation by mononuclear non-heme iron(Il) enzymes, /. Biol. Inorg. Chem. 10 (2005) 87. 

Rieske oxygenases are part of a superfamily of enzymes that share a characteristic structure consisting of an oxygenase component (a mononuclear non-heme iron(II) high spin center containing a 2-His-l-carboxylate facial triad motif in the active site) [31-33]. Besides, the active site contains a reductase component (an Fe2-S2 Rieske center) that delivers electrons from NAD(P)H to the oxygenase center [34]. 

This new heteroscorpionate is a potential building block for copolymers with methylmethacrylate and ethylene glycol dimethacrylate able to mimic the 2-His-l-carboxylate facial triad and capable to produce copolymer-bound manganese and rhenium tricarbonyl complexes.M(CO)3 derivatives (M = Mn or Re) containing two tris(oxazolinyl)phenylborate Hgands (Scheme 25) demonstrated to produce significant structural protection... 

Tiirko u G, Uldemolins CP, Muller R, et al. Bis(3,5-dimethyl-4-vinylpyrazol-l-yl) acetic acid a new heteroscorpionate building block for copolymers that mimic the 2-His-l-carboxylate facial triad. Eur J Inorg Chem. 2010 2962—2974. 

E. Que Jr. - The 2-His-l-carboxylate Eacial Triad a Versatile Platform for Dioxygen Activation by Mononuclear Nonheme Iron (II) Enzymes,... 

In 2-OG dependent enzymes ferrous iron is bound in the active site by the 2-His-l-carboxyIate facial triad. The carboxylate is either an aspartic acid or a glutamic acid. In the beginning the slightly distorted... 

---