Comparison of the mode of action and site specificity of endo-(1,4)-β-d-glucanases of Penicillium pinophilum using normal, 1-3H-labelled, reduced and chromogenic cello-oligosaccharides

K. MAHALINGESHWARA BHAT; AUSTER J. HAY; THOMAS M. WOOD; MARC CLAEYSSENS

doi:10.1042/bst0180638

Comparison of the mode of action and site specificity of endo-(1,4)-β-d-glucanases of Penicillium pinophilum using normal, 1-3H-labelled, reduced and chromogenic cello-oligosaccharides

Biochemical Society Transactions ◽

10.1042/bst0180638 ◽

1990 ◽

Vol 18 (4) ◽

pp. 638-639 ◽

Cited By ~ 1

Author(s):

K. MAHALINGESHWARA BHAT ◽

AUSTER J. HAY ◽

THOMAS M. WOOD ◽

MARC CLAEYSSENS

Keyword(s):

Mode Of Action ◽

Site Specificity ◽

Penicillium Pinophilum

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Study of the mode of action and site-specificity of the endo-(1→4)-β-d-glucanases of the fungus Penicillium pinophilum with normal, 1-3H-labelled, reduced and chromogenic cello-oligosaccharides

Biochemical Journal ◽

10.1042/bj2660371 ◽

1990 ◽

Vol 266 (2) ◽

pp. 371-378 ◽

Cited By ~ 28

Author(s):

K M Bhat ◽

A J Hay ◽

M Claeyssens ◽

T M Wood

Keyword(s):

Cell Membrane ◽

Mode Of Action ◽

Analytical Data ◽

Degree Of Polymerization ◽

The Other ◽

Site Specificity ◽

Glycosidic Bonds ◽

Penicillium Pinophilum ◽

Hydrolysis Of Cellulose ◽

Hydrolysis Of

The modes of action of the five major endo-(1→4)-beta-D-glucanases (I, II, III, IV and V) purified from Penicillium pinophilum cellulase were compared by h.p.l.c. analysis, with normal, 1-3H-labelled and reduced cello-oligosaccharides and 4-methylumbelliferyl glycosides as substrates. Significant differences were observed in the preferred site of cleavage even when substrates with the same number of glycosidic bonds were compared. Thus, although endoglucanase I was unable to attack normal cello-oligosaccharides shorter than degree of polymerization 6, it hydrolysed reduced cellopentaose to yield cellotriose and cellobi-itol, and it produced cellotriose and 4-methylumbelliferyl glucoside from 4-methylumbelliferyl cellotetraoside. Endoglucanase IV hydrolysed [1-3H]cellotriose but did not attack either cellotri-itol or 4-methylumbelliferyl cellobioside. These and other anomalous results indicated clearly that modification of the reducing glycosyl residue on the cello-oligosaccharides induces in an apparent change in the mode of action of the endoglucanases. It is suggested that, although cello-oligosaccharide derivatives are useful for differentiating and classifying endoglucanases, conclusions on the mechanism of cellulase action resulting from these measurements should be treated cautiously. Unequivocal information on the mode of endoglucanase action on cello-oligosaccharides was obtained with radiolabelled cello-oligosaccharides of degree of polymerization 3 to 5. Indications that transglycosylation was a property of the endoglucanases were particularly evident with the 4-methylumbelliferyl cello-oligosaccharides. Turnover numbers for hydrolysis of the umbelliferyl cello-oligosaccharides were calculated, and these, along with the other analytical data collected on the products of hydrolysis of the normal, reduced and radiolabelled cello-oligosaccharides, suggested that the various endoglucanases had different roles to play in the overall hydrolysis of cellulose to sugars small enough to be transported through the cell membrane.

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Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066917 ◽

1971 ◽

Vol 29 ◽

pp. 570-571

Author(s):

E. A. Elfont ◽

R. B. Tobin ◽

D. G. Colton ◽

M. A. Mehlman

Keyword(s):

Chemical Composition ◽

Rat Liver ◽

Future Study ◽

Mode Of Action ◽

Liver Mitochondria ◽

Rat Liver Mitochondria ◽

Effective Inhibitor ◽

Biochemical Effects ◽

Glycerophosphate Dehydrogenase ◽

Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

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