A study of enzymic degradation of a macromolecular substrate, poly[N5-(2-hydroxyethyl)-L-glutamine], by gel permeation chromatography and kinetic modelling.
The enzymatic degradation of poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG) by papain was investigated with the aim of evaluating the role of the random and/or a non-random mechanism of cleavage. The random degradation was modelled experimentally by the reaction of PHEG with ethanolamine. Assuming that different mechanisms of cleavage would yield different molecular weight distributions (MWDs) of the polymer degraded to the same degree, the evaluation was based on the comparison of experimental MWDs, measured by gel permeation chromatography, with MWDs simulated kinetically for the assumed mechanism of degradation. While a very good fit through a broad range of degradation conversions was obtained between the MWDs simulated for a random process and the experimental MWDs of the degradation of PHEG by ethanolamine, the enzymic degradation of PHEG by papain was certainly not a random process. Two models were found to be compatible with the chromatographic data: (i) a multiple attack assuming that the subsequent cleavage may proceed only on one of the two fragments produced by the previous attack, or (ii) a model which assumes that the degradation rate of one bond in a macromolecule of molecular weight M is proportional to M-1/3, i.e. a model which stresses the role of the surface of the polymer coil. In both simulations of enzymic degradation, the two bonds on each end of the PHEG chain were assumed not be cleavable.
Pytela
J
J
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague.
Jakes
J
J
Rypácek
F
F
D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D066298:In Vitro Techniques; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D008970:Molecular Weight; D010206:Papain / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*
D010455:Peptides; C027887:poly-N(5)-(2-hydroxyethyl)glutamine; D010206:Papain