Enzyme Handbook

Schomburg, Dietmar; Salzmann, Margit

doi:10.1007/978-3-642-76729-6_1

Cited by 17 publications

(12 citation statements)

References 2,292 publications

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“…The release pattern of the primary ends from the polymer crystal depends strongly on the end preference of the enzyme, but also on the enzyme concentration and processivity (Figs 7,8). A convex progress curve is obtained from a simulation when the enzyme is defined to act from the labelled end, whereas a …”

Section: Resultsmentioning

confidence: 99%

“…The molecular basis for this latter synergism is not yet understood, mainly because the modes of action of the individual enzymes on crystalline cellulose are not known. By definition, CBHs attack the cellulose chain from the non-reducing end [8]. Recent data indicate, however, that the exhaustively studied Trichoderma reesei 1,4-β-D-glucan-cellobiohydrolase I (CBH I) preferentially attacks the reducing end of cellooligosaccharides, whereas the similarly well-characterised 1,4-β-D-glucan-cellobiohydrolase II (CBH II) from the same organism indeed prefers the non-reducing end [9,10].…”

mentioning

confidence: 99%

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Nutt

Sild²,

Pettersson³

et al. 1998

European Journal of Biochemistry

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The chain-end preference and processivity of the cellulases 1,4-β-D-glucan-cellobiohydrolase I (CBH I) and 1,4-β-D-glucan-cellobiohydrolase II (CBH II) from Trichoderma reesei and 1,4-β-D-glucancellobiohydrolase 50 (CBH 50) and 1,4-β-D-glucan-cellobiohydrolase 58 (CBH 58) from Phanerochaete chrysosporium were studied by comparing experimental degradation data on reducing end-labelled bacterial microcrystalline cellulose with computer simulations of different models. Our results with T. reesei and P. chrysosporium cellulases show that there is a common pattern of hydrolysis for CBH-I-type enzymes and another clearly distinguishable pattern for CBH-II-type enzymes, especially in the initial part of the progress curve.Keywords : cellulase ; cellulose; hydrolysis ; simulation ; mode of action.In nature, the breakdown of cellulose is carried out mainly by fungi and bacteria. These organisms degrade crystalline cellulose by means of several enzymes acting at the ends (exocellulases) or randomly (endoglucanases) on the cellulose chains. Cellulases, like many other enzymes attacking insoluble or 'larger-than-enzyme' polymeric substrates, have a characteristic two-domain organisation : a catalytic domain connected by a flexible linker to a separate cellulose-binding domain [1]. Effective degradation of native cellulose requires cooperation between different functional types of cellulases and displays two distinctive modes of synergism; namely, cooperation among endoglucanases and cellobiohydrolases (CBHs) (endo/exo synergism), where the endoglucanases are supposed to create a large number of free ends susceptible to exoglucanase action [2Ϫ4], and cooperation among different CBHs [5Ϫ7]. The molecular basis for this latter synergism is not yet understood, mainly because the modes of action of the individual enzymes on crystalline cellulose are not known. By definition, CBHs attack the cellulose chain from the non-reducing end [8]. Recent data indicate, however, that the exhaustively studied Trichoderma reesei 1,4-β-D-glucan-cellobiohydrolase I (CBH I) preferentially attacks the reducing end of cellooligosaccharides, whereas the similarly well-characterised 1,4-β-D-glucan-cellobiohydrolase II (CBH II) from the same organism indeed prefers the non-reducing end [9,10].

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Progress curves

Nutt

Sild²,

Pettersson³

et al. 1998

European Journal of Biochemistry

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“…typical of horseradish peroxidase (Schomburg, Salzmann & Stephan, 1994), two protein bands of c. 38 and 40 kDa were observed. In a control experiment, a severe bacterial infection in an aliquot of purified root exudate added no further protein bands of c. 40 kDa, but additional proteins were observed in the region of 16 kDa.…”

Section: Peroxidase Isoforms In Sterile Root Exudates Of Alfalfamentioning

confidence: 92%

“…Efficient production of Mn$ + from Mn# + in the presence of H # O # is normally ascribed to manganese peroxidase. This enzyme owes its ligninolytic capacity to the formation of Mn$ + and has so far been studied only in fungal systems (Schomburg et al, 1994). Formation of Mn$ + can also be initiated by phenoxy and aryloxy radicals that had been formed from phenolic substrates by HRP (Kenten & Mann, 1950), laccase (Archibald & Roy, 1992), or lignin peroxidase (Popp, Kalyanaraman & Kirk, 1990).…”

Section: mentioning

confidence: 99%

Activities of oxidoreductase enzymes in tissue extracts and sterile root exudates of three crop plants, and some properties of the peroxidase component

Gramss

Rudeschko

1998

New Phytologist

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Aqueous extracts of homogenized shoot and root tissue of alfalfa (Medicago sativa L.), white mustard (Sinapis alba L.), and cress (Lepidium sativum L.), with the exudates of sterile roots of these crop plants, were examined spectrophotometrically for the activities of 20 oxidoreductase enzymes by standard procedures. In tissue extracts and root exudates, the reactions of laccase (EC 1;10;3;2), ascorbate oxidase (EC 1;10;3;3), monophenol monooxygenase (EC 1;14;18;1), and phenol 2-monooxygenase (EC 1;14;13;7) were readily detected. Of the aromatic-ring cleavage dioxygenases, those of the meta-cleavage pathway (EC 1;13;11;2 and 1;13;11;8) could also be detected. Guaiacol peroxidase (EC 1;11;1;7) was dominant in all samples. In sterile root exudates of alfalfa, this enzyme was represented by at least seven acidic isoforms. The formation of the ligninolytic Mn$ + \malonate and Mn$ + \citrate complexes from Mn# + occurred in all tissue extracts and in root exudates of alfalfa. In root extracts of soybean (Glycine max L.), the rate of Mn$ + generation correlated (P l 0n993) with the activities of endogenous plant guaiacol peroxidase and horseradish peroxidase (HRP) supplements and also with the total phenol content in tissue extracts (P l 0n984). Plant guaiacol peroxidase and purified HRP decolorized four aromatic dyes, an activity reported to be involved in ligninolysis. Although no enzymes capable of generating H # O # as a consequence of the oxidation of simple sugars, amino acids, organic acids, and aldehydes were found, traces of peroxide were detected in tissue extracts and in the root exudate of alfalfa. It is concluded that the oxidoreductases found in plant tissues also occur in root exudates of aseptic whole plants. The significance of interrelations between oxidoreductase enzymes and enzymically generated higher-valency metal ions is discussed in the context of the oxidative conversion of phenolic compounds in soil and plant tissue.

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“…The definition of EC 3+1+26 is "Hydrolases; Acting on ester bonds; Endoribonucleases producing 59-phosphomonoesters+" The current definition of RNase P, EC 3+1+26+5, is: "Recommended name: ribonuclease P; Reaction: Endonucleolytic cleavage of RNA, removing 59-extranucleotides from tRNA precursor; Comments: An RNA-containing enzyme, essential for tRNA processing; generates 59-termini of mature tRNA molecules" (NC-IUBMB, 1992; p+ 342; Schomburg & Salzmann, 1991)+ Clearly, these reaction specifications identify any pre-tRNA 59-maturation endoribonuclease that acts as a true hydrolase rather than a phosphoryltransferase+ The possession of an RNA subunit is not a formal part of the enzyme definition+…”

Section: Canonical and Non-canonical Rnase Pmentioning

confidence: 99%

Enzyme nomenclature: Functional or structural?

Gegenheimer

2000

RNA

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Enzyme Handbook

Cited by 17 publications

References 2,292 publications

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Activities of oxidoreductase enzymes in tissue extracts and sterile root exudates of three crop plants, and some properties of the peroxidase component

Enzyme nomenclature: Functional or structural?

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