Cellulose enzymic analysis

In Escherichia coli. Salmonella typhimurium and Aerobacter aerogenes two soluble multi-activity enzymes or enzyme complexes function in the utilisation of chorismate (14) for L-phenyl-alanine and L-tyrosine synthesis An enzyme or enzyme complex (P-protein) containing chorismate mutase and prephenate dehydratase activities has been isolated and partially purified from Escherichia coli. Salmonella typhimurium and Aerobacter aerogenes. The enzyme complex catalyses the transformation of chorismate (14) to phenylpyruvate (32) and both enzymic activities are retained in physical association after chromatography on DEAE cellulose. Kinetic analysis indicated that in isolated enzyme systems direct synthesis of phenylpyruvate (32) from chorismate (14) does not occur. Prephenate (31) once formed dissociates from the enzyme surface and accumulates in the reaction medium. After a lag period it is converted to phenylpyruvate (32). Schmit, Artz and Zalkin also obtained evidence to show that functionally distinct sites (catalytic and regulatory) exist on the P-protein from Salmonella typhimurium for chorismate mutase and prephenate dehydratase activities. The P-protein was obtained from Escherichia coli K-12 by Davidson, Blackburn and Dopheide who showed that it existed in solution mainly as a dimer of similar (and probably identical) sub-units of... 

Current data indicate that the analysis of cellulase enzyme activities may be the best method for determining the projected cellulose conversion of the overall system, and therefore the hydrolytic power of the system under evaluation. With development, the analysis of enzyme activities may also serve as a "real time" method of monitoring the stability of the system, with radical changes in enzyme activities indicative of potential process upset. 

In an attempt to separate the domains from the cores, we used limited degradation with several proteases. CBH I (65 kda) and CBH II (58 kda) under native conditions could only be cleaved successfully with papain (15). The cores (56 and 45 kda) and terminal peptides (11 and 13 kda) were isolated by affinity chromatography (15,16) and the scission points were determined unequivocally. The effect on the activity of these enzymes was quite remarkable (Fig. 7). The cores remained perfectly active towards soluble substrates such as those described above. They exhibited, however, a considerably decreased activity towards native (microcrystalline) cellulose. These effects could be attributed to the loss of the terminal peptides, which were recognized as binding domains, whose role is to raise the relative concentration of the intact enzymes on the cellulose surface. This aspect is discussed further below. The tertiary structures of the intact CBH I and its core in solution were examined by small angle X-ray scattering (SAXS) analysis (17,18). The molecular parameters derived for the core (Rj = 2.09 mm, Dmax = 6.5 nm) and for the intact CBH I (R = 4.27 nm, Dmax = 18 nm) indicated very different shapes for both enzymes. Models constructed on the basis of these SAXS measurements showed a tadpole structure for the intact enzyme and an isotropic ellipsoid for the core (Fig. 8). The extended, flexible tail part of the tadpole should thus be identified with the C-terminal peptide of CBH I. 

A given microorganism may produce one or more enzymes of each type. An understanding of the role of each enzyme in cellulose biodegradation requires their purification and characterization, and an analysis of the ways in which they interact with the substrate and with each other. However, it is often quite difficult to determine the number and type of truly different enzymes produced by an organism. Many cellulolytic microorganisms secrete proteases, which may degrade some or all of the cellulases to smaller,... 

The extracellular polysaccharides of Rhizobium meliloti 201 have been examined by using enzymic degradation and chemical procedures.314 A mixture of polysaccharides produced by the bacterium, when incubated with a bacterial enzyme that hydrolyzed one of these, gave oligosaccharides that could be separated by DEAE-cellulose chromatography. The major fraction was a pentasaccharide, for which methylation analysis and Smith... 

The electron micrographs of the enzyme-treated sprucewood holo-cellulose revealed the loci of the removed substances when compared with untreated samples. The relative intensity of degradation at the ultra-structural level corresponded to the results obtained by chemical analysis of the dissolved carbohydrates. 

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