Stability of native and covalently modified papain.


By jpeza - Posted on 11 Noviembre 2010

Fecha Publicación: 
1 Oct 1995
Nombre de Revista: 
Datos del paper
Autor Principal: 
Rajalakshmi
N
Volumen: 
8
Issue: 
10 1039
Página Inicial: 
1039
Página Final: 
1047
Abstract: 

Covalent modification of enzymes with large polymers can produce
modified enzymes which retain considerable biological activity
and at the same time display resistance to
denaturation by high temperatures and chaotropic agents. The cysteine
protease,
papain, with potential applications in industry,
was covalently coupled to polymeric sucrose (mol. wt 400 kDa) at
different
ratios. The derivatives retained >80% intrinsic
catalytic activity with no change in pH optima and kinetic constants,
indicating
that the gross tertiary structure was not altered
by modification. However, they displayed better thermotolerance than
native
papain, as indicated by their higher T50
values (6–10°C) and their temperature optima being shifted by 10°C. The
half-life of modified papain, calculated from the
rate of thermoinactivation, was prolonged by 2- to
30-fold over the native depending on the temperature and proportion of
polymeric sucrose in the adducts. The increases in
activation free energy of inactivation (1–10 kj/mol) and activation
enthalpy
(4‐78 kj/mol) indicate stabilization of the protein
and lesser inactivation due to spontaneous unfolding. In the presence
of urea, modified papain showed activation, which
may be due to a loosening of the ‘rigid’ structure, reminiscent of the
property
of thermophilic enzymes.

Dirección del Autor: 

Centre for Protein Engineering and Biomedical Research, The Voluntary Health Services Madras 600 113, India

Keywords: 
covalent modification ; free energy measurements ; papain ; thermal inactivation
Coautores: 
  1. P. V. Sundaram1
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