Abstract: The invention provides chemically modified proteins having a group of the formula: ##STR1## wherein R represents a hydrogen atom or a lower alkyl, m represents an optional positive integer and n represents an integer 1 to 4, the group being bonded to at least one primary amino group of the protein, and a method of producing the same. The chemically modified proteins according to the invention can be produced by reacting a protein with an imidoester of the formula: ##STR2## wherein R, n and m are as defined above, R' represents a group constituting an imidoester with an adjacent imidoyl group. The chemically modified proteins according to the invention are useful as drugs, among others.

Abstract: The invention provides a compound of the formula (I): R--O--CH.sub.2 CH.sub.2 O.sub.m CH.sub.2).sub.n --Z wherein R is a glycosyl group, m is an optional positive integer, n is an integer from 1 to 3 and Z is --CHO, --CH.sub.2 OH or --COOH.The compound of the formula (I'): R--O--CH.sub.2 CH.sub.2 O.sub.m CH.sub.2).sub.n --CHO wherein R, m and n are as defined above and the formula (I"'): R--OCH.sub.2 CH.sub.2 O.sub.m CH.sub.2).sub.n --COOH wherein R, m and n are as defined above is useful as a chemically modifying agent for protein.The compound of the formula (I"): R--O--CH.sub.2 CH.sub.2 O.sub.m CH.sub.2).sub.n --CH.sub.2 OH wherein R, m and n are as defined above is useful as a protein fractionating agent.

Abstract: A novel peptide-enzyme conjugate obtained by coupling a labeling enzyme with a peptide of the general formula:H-R.sub.1 -Phe-Val-Gln-Trp-Leu-R.sub.2 -Asn-Thr-OH(wherein R.sub.1 is a peptide fragment consisting of 1 to 10 amino acid residues in the sequence of and including the Asp in 10-position of ##STR1## and R.sub.2 is Met or Nle) is useful for a method for enzyme immunoassay of pancreatic glucagon.