Modified DNase I protein in which one or more amino acids of a DNase I protein are modified non-cellularly, are provided. The modified DNase I protein exhibits a DNA hydrolytic activity in the presence of actin and an improved DNA hydrolytic activity compared to a homologous non-modified DNase I protein. Processes of preparing the modified DNase I protein and uses thereof in, for example, reducing a DNA content in sputum and/or in treating a disease or condition associated with excess extracellular DNA in a fluid, secretion or tissue of a subject, are also provided.
