The role of the ε-amino groups of lysine in the origin of the polarographic waves of proteins
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A preparation of 70% acetylated lysozyme was obtained. It was shown by various methods (gel filtration, electrophoresis, UV spectroscopy, determination of activity) that there were no significant denaturation changes in the structure of acetylated lysozyme.
In polarography, the acetylated protein does not exhibit any significant differences in behavior on a mercury cathode in the range of pH from 5.5 to 10.5. Apparently the free amino groups are not a necessary component in the complexes responsible for the appearance of a two-step catalytic wave.
A comparative study was made of acetylated and native lysozyme with, the aid of oscillographic polarography. Under all the investigated conditions, for the acetylated protein the catalytic waves and wave of cobalt bound in a complex with protein are lower, while the wave of free cobalt is higher than for the native protein.
An analysis was made of the causes of the different sensitivity to blocking of the amino groups in proteins and low-molecular compounds. The large excess of protein on the surface of the cathode, formed as a result of strong irreversible adsorption of it, becomes the cause of the fact that the catalytic complex cannot contain the amino groups essential for catalysis.
The significant role of the ε-amino groups of lysine in the origin of the third catalytic “presodium” wave of the protein was confirmed.
KeywordsMercury Cobalt Lysine Lysozyme Free Amino
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