6WIA

CRYSTAL STRUCTURE OF HUMAN PROTECTIVE PROTEIN/CATHEPSIN A, DFP-INHIBITED (AGED)

Summary for 6WIA

• Entry DOI: 10.2210/pdb6wia/pdb
• Descriptor: Lysosomal protective protein, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, ACETATE ION, ... (6 entities in total)
• Functional Keywords: lysosomal, cathepsin a, cata, ctsa, organophosphate, renin-angiotensin system (ras), hydrolase
• Biological source: Homo sapiens (Human)
• Total number of polymer chains: 1
• Total formula weight: 54317.49

Authors

Compton, J.R.,Legler, P.M. (deposition date: 2020-04-09, release date: 2020-04-29, Last modification date: 2023-10-18)

Primary citation

Bouknight, K.D.,Jurkouich, K.M.,Compton, J.R.,Khavrutskii, I.V.,Guelta, M.A.,Harvey, S.P.,Legler, P.M.
Structural and kinetic evidence of aging after organophosphate inhibition of human Cathepsin A.
Biochem. Pharmacol., 177:113980-113980, 2020

PubMed Abstract: Human Cathepsin A (CatA) is a lysosomal serine carboxypeptidase of the renin-angiotensin system (RAS) and is structurally similar to acetylcholinesterase (AChE). CatA can remove the C-terminal amino acids of endothelin I, angiotensin I, Substance P, oxytocin, and bradykinin, and can deamidate neurokinin A. Proteomic studies identified CatA and its homologue, SCPEP1, as potential targets of organophosphates (OP). CatA could be stably inhibited by low µM to high nM concentrations of racemic sarin (GB), soman (GD), cyclosarin (GF), VX, and VR within minutes to hours at pH 7. Cyclosarin was the most potent with a kinetically measured dissociation constant (K) of 2 µM followed by VR (K = 2.8 µM). Bimolecular rate constants for inhibition by cyclosarin and VR were 1.3 × 10 Msec and 1.2 × 10 Msec, respectively, and were approximately 3-orders of magnitude lower than those of human AChE indicating slower reactivity. Notably, both AChE and CatA bound diisopropylfluorophosphate (DFP) comparably and had K = 13 µM and 11 µM, respectively. At low pH, greater than 85% of the enzyme spontaneously reactivated after OP inhibition, conditions under which OP-adducts of cholinesterases irreversibly age. At pH 6.5 CatA remained stably inhibited by GB and GF and <10% of the enzyme spontaneously reactivated after 200 h. A crystal structure of DFP-inhibited CatA was determined and contained an aged adduct. Similar to AChE, CatA appears to have a "backdoor" for product release. CatA has not been shown previously to age. These results may have implications for: OP-associated inflammation; cardiovascular effects; and the dysregulation of RAS enzymes by OP.

PubMed: 32305437
DOI: 10.1016/j.bcp.2020.113980

Experimental method

X-RAY DIFFRACTION (2.21 Å)