Surface Modification of Cellulose Acetate with Cutinase and ...

General Introduction: Application of Enzymes for Textile Fibres Processing
have been tested at the scale of industrial process (Shen et al., 2007). Pre-treatment of
wool fibres with hydrogen peroxide, at alkaline pH in the presence of high
concentrations of salts, also targets enzymatic activity on the outer surface of wool, by
improving the susceptibility of cuticle for proteolytic degradation (Lenting et al., 2006).
Some authors describe methods to improve the shrink resistance of wool by treating
wool previously with a smoother oxidizing agent, like H2O2, instead of the traditional
oxidizers, NaClO or KMnO4 and then with a protease (Yu et al., 2005). The strong
oxidation power of NaClO or KMnO4 is always difficult to control. Besides, reaction of
NaClO with wool produces halogenide. On the other hand, H2O2 seemed to provide a
more controlled, cleaner and moderate oxidation. Zhang and collaborators used an
anionic surfactant to promote the activities of proteases on wool (Zhang et al., 2006).
Other authors refer processes to achieve shrink-resistance by treating wool with a
protease followed by a heat treatment (Ciampi et al., 1996). The screening for new
protease producing microorganisms with high specificity to cuticles is being
investigated as an alternative for the existing proteases (Erlacher et al., 2006).
8. Cysteine proteases: papain
Cysteine proteases (CP´s) catalyse the hydrolysis of peptide, amide, ester, thiol ester
and thiono ester bonds. More than twenty families of cysteine proteases have been
described (Barrett, 1994). The CP family can be subdivided into exopeptidases (e.g.
cathepsin X, carboxypeptidase B) and endopeptidases (papain, bromelain, ficain,
cathepsins). Exopeptidases cleave the peptide bond proximal to the amino or carboxy
termini of the substrate, whereas endopeptidases cleave peptide bonds distant from the
N- or C-termini (Barrett, 1994).
CPs are proteins of molecular mass in the range of 21 - 30 kDa. They are synthesized as
inactive precursors with an N-terminal propeptide and a signal peptide. Activation
requires proteolytic cleavage of the N-terminal propeptide that also functions as an
inhibitor of the enzyme (Otto and Schirmeister, 1997; Grzonka et al., 2001).
Papain is the best known cysteine protease. It was isolated in 1879 from the fruits of
Carica papaya and was the first protease with the crystallographic structure determined
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