Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1998-10-13
2001-10-09
Mullis, Jeffrey (Department: 1711)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S057000, C536S076000, C536S124000, C435S072000, C435S101000
Reexamination Certificate
active
06300493
ABSTRACT:
TECHNICAL FIELD
This invention relates to methods and compositions for modification of polysaccharide characteristics using polysaccharidases and/or their functional domains. The method is exemplified by the use of an isolated cellulose binding domain of a bacterial endoglucanase to disrupt the structure of cellulose fibers and the use of an isolated catalytic domain of this enzyme to polish the surface of the fibers.
BACKGROUND
Polysaccharides are ubiquitous, stable structural components found in nature. Many organisms use polysaccharides as structural material inside and outside of their cells to provide 3-dimensional shape and surface structure. The structural integrity of polysaccharides from natural sources is often retained after the isolation of the polysaccharide, allowing it to be used for a variety of commercial purposes. Owing to their desirable physical characteristics polysaccharides have also been produced by synthetic methods for commercial purposes. In either case, polysaccharides from either synthetic or non-synthetic sources comprise the raw material for a variety of commercially important products such as paper pulp, agricultural produce and fibers.
Polysaccharide structures generally are stable and relatively inert to a variety of chemical conditions. This gives both non-synthetic and synthetic products prepared from polysaccharide structures the desirable characteristics of durability, strength and resistance to aging. However, raw or unprocessed polysaccharidic structures often have undesirable characteristics due to precisely the same physical properties that give them their desirable characteristics. The undesirable characteristics generally include coarse texture, inflexibility, hardness, and abrasiveness, although for some applications some of these characteristics may be preferred. Such traits are particularly common for raw, natural fibers that have not been processed.
Methods do exist to refine and alter the structure of polysaccharides used for commercial products which include mechanical disruption, polishing, washing and spinning of fibers into finer threads and materials. However, it would be of interest to develop an alternative approach to mechanically polishing natural and synthetic polysaccharide structures to facilitate refining of polysaccharide structures, particularly in a predictable, specific fashion. Such refinements could include changing the texture, appearance, touch and feel of the polysaccharide structure.
RELEVANT LITERATURE
Two cellulases from
C. fimi,
an exoglucanase (Cex) and an endoglucanase (CenA), have been characterized and their genes, cex and cenA, respectively, have been sequenced (Wong et al.,
Gene
(1986) 44:315-324; O'Neill et al.,
Gene
(1986) 44:325-330). Predicted amino acid sequences show evidence of domain structure for these enzymes (Warren et al.,
PROTEINS: Structure, Function, and Genetics
(1986) 1:335-341). Several cellulose genes from
Cellulomonas fimi
have been cloned into
Escherichia coli
(Whittle et al.,
Gene
(1982) 17:139-145; Gilkes et al.,
J. Gen. Microbiol.
(1984) 130:1377-1384) and the gene fragment encoding the cellulose binding domain and the cellulose binding domain connected to the PT box of CenA have been cloned in
E. coli.
(Gilkes, et al. 1988).
Domain structures have also been observed in other cellulases (Teeri et al.,
Publications
(1987) 38: Technical Research Centre of Finland; Teeri et al.,
Gene
(1987) 51:43-52) and separation of domains by proteolytic cleavage has given some insight into domain function (Langsford et al.,
FEBS Letters
(1987) 225:163-167; Tomme et al.,
Eur. J. Biochem.
(1988) 170:575-581; van Tilbeurgh et al.,
FEBS Letters
(1986) 204:223-227). See also Kellet, et al.,
Biochem J.
(1990) 272: 369-376, Watanabe, et al.
J. Biol Chem
(1990) 265; 15659-15665, Svensson, et al.,
Biochem J.
(1989) 264: 309-311, and Takahashi, et al.).
SUMMARY OF THE INVENTION
The present invention provides methods and compositions for modification of polysaccharide structures using functional domains of polysaccharidases. The method includes the step of contacting a polysaccharide structure with a sufficient amount of a functional domain obtainable from a polysaccharidase under conditions and for a time sufficient to modify a characteristic of the polysaccharide. The surface area of the polysaccharide structure may be roughened by using a binding domain whereas the surface may be smoothed by using a catalytic domain. The methods and compositions find use in producing polysaccharide structures with altered mechanical or physical properties.
REFERENCES:
patent: 4479881 (1984-10-01), Tai et al.
patent: 4738682 (1988-04-01), Boegh et al.
patent: 4822516 (1989-04-01), Suzuki et al.
patent: 5821358 (1998-10-01), Gilkes et al.
patent: 773280 (1972-03-01), None
patent: 0 290 027 (1988-11-01), None
patent: 1368599 (1974-10-01), None
patent: WO 91/10732 (1991-07-01), None
Gilkes Neil R.
Kilburn Douglas G.
Miller, Jr. Robert C.
Warren Anthony
Mullis Jeffrey
Rae-Venter Barbara
Rae-Venter Law Group P.C.
University of British Columbia
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