A protein produced by gene recombinant technology, including at least one domain selected from domains I, II, and III of serum albumin but having a different structure from that of native albumin; and a method of producing the protein. The protein has an enhanced functional activity or activities selected from among various functional activities or serum albumin including antibacterial activity, antioxidative effect, inflammation inhibitory effect, in vivo substance transporting action, and enzymatic activity.