Catalase crystal structure

Scheme 8. A proposed mechanism for the disproportionation of hydrogen peroxide by manganese catalase, based on the mechanism proposed by Penner-Hahn in 1992, and the T. thermophilus catalase crystal structure. [Adapted with permission from (24). Copyright 1992 WILEY-VCH Verlag.]...

Fig. 9. Contoured intensities of the catalase crystal structure using computer-enhanced electron microscope images. ...

Bertrand T, NAJ Eady, IN Jones, Jesmin, JM Nagy, B Jamart-Gregoire, EL Raven, KA Brown (2004) Crystal structure of Mycobacterium tuberculosis catalase-peroxidase. J Biol Chem 279 38991-38999. 

Barynin, V.V., Whittaker, M.M., Antonyuk, S.V., Lamzin, V.S., Harrison, P.M., Artymiuk, PJ. and Whittaker, J.W. (2001) Crystal structure of manganese catalase from Lactobacillus plantarum,... 

The tertiary structure of small subunit enzymes can be subdivided into four distinct regions, and the C-terminal or flavodoxin domain of the large subunit enzymes becomes a fifth region. These are indicated in Fig. 8 for clarity. The first region is the amino terminal arm (Fig. 8), which extends 50 or more residues from the amino terminus almost to the essential histidine residue (to residue 53 in PMC, 60 in PVC, 73 in BLC, and 127 in HPII). There is very little structural similarity in the N-terminal region and, in the case of HPII, the structure of the terminal 27 residues is not even defined and they do not appear in the crystal structure. Within the N-terminal arm is a 20-residue helix, helix a2 in HPII, which is the first secondary structure element common to all catalases. The presence of helix al varies among catalases, and there is no sequence or location equivalence even when it is present. 

Catalases continue to present a challenge and are an object of interest to the biochemist despite more than 100 years of study. More than 120 sequences, seven crystal structures, and a wealth of kinetic and physiological data are currently available, from which considerable insight into the catalytic mechanism has been gained. Indeed, even the crystal structures of some of the presumed reaction intermediates are available. This body of information continues to accumulate almost daily. 

The catalase-peroxidases present other challenges. More than 20 sequences are available, and interest in the enzyme arising from its involvement in the process of antihiotic sensitivity in tuherculosis-causing bacteria has resulted in a considerable body of kinetic and physiological information. Unfortunately, the determination of crystallization conditions and crystals remain an elusive goal, precluding the determination of a crystal structure. Furthermore, the presence of two possible reaction pathways, peroxidatic and catalatic, has complicated a definition of the reaction mechanisms and the identity of catalytic intermediates. There is work here to occupy biochemists for many more years. 

Crystal structures of manganese catalases (in the (111)2 oxidation state) from Lactobacillus plantarum,its azide-inhibited complex, " and from Thermus thermophilus have been determined. There are differences between the structures that may reflect distinct biological functions for the two enzymes, the L. plantarum enzyme functions only as a catalase, while the T. thermo-philus enzyme may function as a catalase/peroxidase. The active sites are conserved in the two enzymes and are shown schematically in Figure 32. Each subunit contains an Mu2 active site,... 

The Mn complexes of dicarboxylic acids are efficient catalase mimics. The crystal structure of [MnII(ri1ri1-L4)(phen)2] 28, (L4 = cA-5-norbomene-e cfo-2,3,-dicarboxylic acid and phen = 1,10-phenanthroline) (Figure 13) shows that this complex is a water linked dinuclear compound in solid state [100n],... 

The crystal structure for the T. thermophilus Mn catalase (21) shows that this protein has a structure containing four parallel alpha-helices, similar to the structure found in dinuclear Fe proteins such as hem-... 

These are difficult enzymes to work with and only recently have crystal structures become available for two catalase-peroxidases Haloarcula marismortui (HMCP) and Burkholderia pseudomallei (BpKatG). A typical subunit is approximately 80 kDa in molecular mass, with a single heme b prosthetic group. The primary structure of each subunit can be divided into two distinct domains, N terminal and C terminal. The N-terminal domain contains the heme and active site, while the C-terminal domain does not contain a heme binding motif and its function remains unclear. The clear sequence similarity between the two domains suggests gene duplication and fusion. Curiously, despite many years of study, the actual in vivo peroxidatic substrate of the catalase-peroxidases has not been identified. 

Mn catalase cycles between the Mn /Mfo and the Mn /Mn oxidation states during catalysis and is thus, in some sense, the two-electron analog of Mn superoxide dismutase. One possible mechanistic model, based on the known coordination chemistry of Mn dimers and the crystal structures of Mn catalase, is shown in Scheme 3. In this scheme, the bridging solvent molecules play a critical role in... 

Most catalases consist of four subunits of 60,000 mol each and contain one ferri-protoporphyrin IX molecule per subunit. With few exceptions, catalases are found in all but anaerobic organisms. The crystal structure of beef liver catalase has been determined to 2.5 pm resolution ", and the primary sequence is also known. ... 

X-ray crystal structures have been determined for beef-liver catalase and for horseradish peroxidase in the resting, high-spin ferric state. In both, there is a single heme b group at the active site. In catalase, the axial ligands are a... 

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