1QIX

Porcine pancreatic elastase complexed with human beta-casomorphin-7

Summary for 1QIX

• Entry DOI: 10.2210/pdb1qix/pdb
• Related: 3EST
• Descriptor: BETA-CASOMORPHIN-7, ELASTASE, CALCIUM ION, ... (5 entities in total)
• Functional Keywords: serine proteinase, hydrolase (serine proteinase)
• Biological source: SUS SCROFA (PIG); More
• Cellular location: Secreted: P00772
• Total number of polymer chains: 2
• Total formula weight: 26928.17

Authors

Wilmouth, R.C.,Clifton, I.J.,Hajdu, J.,Schofield, C.J. (deposition date: 1999-06-18, release date: 1999-12-14, Last modification date: 2023-12-13)

Primary citation

Wilmouth, R.C.,Clifton, I.J.,Robinson, C.V.,Roach, P.L.,Aplin, R.T.,Westwood, N.J.,Hajdu, J.,Schofield, C.J.
Structure of a Specific Acyl-Enzyme Complex Formed between Beta-Casomorphin-7 and Porcine Pancreatic Elastase
Nat.Struct.Biol., 4:456-, 1997

PubMed Abstract: Mass spectrometric screening reveals that an unmodified natural heptapeptide--human beta-casomorphin-7, an internal sequence of human beta-casein that possesses opioid-like activity--reacts with porcine pancreatic elastase to form an unusually stable acyl-enzyme complex at low pH. X-ray crystallographic analysis (to 1.9 A resolution) at pH 5 shows continuous electron density linking the C-terminal isoleucine of beta-casomorphin-7 to Ser 195 through an ester bond. The structure reveals a well defined water molecule (Wat 317), equidistant between the carbon of the ester carbonyl and N epsilon 2 of His 57. Deprotonation of Wat 317 will produce a hydroxide ion positioned to attack the ester carbonyl through the favoured Bürgi-Dunitz trajectory.

PubMed: 9187653
DOI: 10.1038/NSB0697-456

Experimental method

X-RAY DIFFRACTION (1.9 Å)