ENHANCED REACTIVITY OF LYSOZYME WITH FORMALDEHYDE DURING COLD DENATURATION

The reactivity of lysozyme with formaldehyde at low temperatures (0 to -20 degrees C) was compared with lysozyme reactivity at 37 degrees C. Lysozyme reaction with formaldehyde, in the presence and absence of s odium cyanoborohydride, was also compared. The progress of reactions w as evaluated by measurement of protein primary amino groups, lysozyme enzymatic activity, and occurrence of cross-linkage as evidenced by so dium dodecyl sulfate-polyacrylamide gel electrophoresis. Results obtai ned indicated that the chemical modification of lysozyme by formaldehy de was significantly enhanced at cold freezing temperatures (-6 and -1 0 degrees C) when compared with 37 degrees C. Cold-temperature protein modification with formaldehyde gave rise to inactive enzyme which was partially cross-linked. Reductive methylation at 37 degrees C did not appreciably affect enzyme activity or cause protein cross-linkage. Ta ken together, these results gave a strong indication that the observed enhanced reactivity of lysozyme with formaldehyde at low temperature was likely due to cold denaturation of the protein.