The invention provides deimmunized mutant proteins having reduced immunogenicity while exhibiting substantially the same or greater biological activity as the proteins of interst from which they are derived, as exemplified by mutant L-asparaginase that comprises amino acid substitutions compared to wild type L-asparaginase. The invention further provides methods for screening mutant deimmunized proteins that have substantially the same or greater biological activity as a protein of interest, and methods for reducing immunogenicity, without substantially reducing biological activity, of a protein of interest.The inventions compositions and methods are useful in, for example, therapeutic applications by minimizing adverse immune responses by the host mammalian subjects to the protein of interest. Thus, the invention further provides methods for treating disease comprising administering to a subject a therapeutically effective amount of a pharmaceutical composition comprising at least one of the mutant deimmunized proteins produced by the inventions methods.