Preferred Label : amino-acid residue;
Detailed label : amino-acid residue in a polypeptide;
IUPAC definition : When two or more amino acids combine to form a peptide, the elements of water are
removed, and what remains of each amino acid is called an amino-acid residue. α-Amino-acid
residues are therefore structures that lack a hydrogen atom of the amino group ( div
class chemoverlay pop pop1 img A00279-1.png –NH–CHR–COOH /div ), or the hydroxyl moiety
of the carboxyl group ( div class chemoverlay pop pop2 img A00279-2.png NH sub 2 /sub
–CHR–CO– /div ), or both ( div class chemoverlay pop pop3 img A00279-3.png –NH–CHR–COO–
/div ); all units of a peptide chain are therefore amino-acid residues. (Residues
of amino acids that contain two amino groups or two carboxyl groups may be joined
by isopeptide bonds, and so may not have the formulas shown.) The residue in a peptide
that has an amino group that is free, or at least not acylated by another amino-acid
residue (it may, for example, be acylated or formylated), is called N-terminal; it
is at the N-terminus. The residue that has a free carboxyl group, or at least does
not acylate another amino-acid residue, (it may, for example, acylate ammonia to give
div class chemoverlay pop pop4 img A00279-4.png –NH–CHR–CO–NH sub 2 /sub /div ),
is called C-terminal.;
Origin ID : A00279;
See also
When two or more amino acids combine to form a peptide, the elements of water are
removed, and what remains of each amino acid is called an amino-acid residue. α-Amino-acid
residues are therefore structures that lack a hydrogen atom of the amino group ( div
class chemoverlay pop pop1 img A00279-1.png –NH–CHR–COOH /div ), or the hydroxyl moiety
of the carboxyl group ( div class chemoverlay pop pop2 img A00279-2.png NH sub 2 /sub
–CHR–CO– /div ), or both ( div class chemoverlay pop pop3 img A00279-3.png –NH–CHR–COO–
/div ); all units of a peptide chain are therefore amino-acid residues. (Residues
of amino acids that contain two amino groups or two carboxyl groups may be joined
by isopeptide bonds, and so may not have the formulas shown.) The residue in a peptide
that has an amino group that is free, or at least not acylated by another amino-acid
residue (it may, for example, be acylated or formylated), is called N-terminal; it
is at the N-terminus. The residue that has a free carboxyl group, or at least does
not acylate another amino-acid residue, (it may, for example, acylate ammonia to give
div class chemoverlay pop pop4 img A00279-4.png –NH–CHR–CO–NH sub 2 /sub /div ),
is called C-terminal.
