Patent ID: 7799549

Claim:
A protein modified by a method which comprises: a) a first step of coupling at least one amino group of a protein with a non-protein polymer to form a first modified protein having one or more non-protein polymer chains; b) a second step of coupling said first modified protein having one or more non-protein polymer chains with an amino group of a polyfunctional amine having at least two amino groups to form a modified protein having one or more additional amino groups, wherein said coupling occurs via carboxyl amidation of said polyfunctional amine to at least one amino acid of the protein; and c) a third step of coupling one or more additional amino groups of said modified protein having one or more additional amino groups with another non-protein polymer to form a second modified protein having more non-protein polymer chains than the first-modified protein, wherein said protein is methioninase, and wherein said modified protein is formed without crosslinking between the first modified proteins.