Enzymes that cleave off lipid modifications on proteins
Protein family
Crystal structure of human APT1, PDB code 1fj2. Alpha helices are in red, beta strands in gold, catalytic site residues in black. The 2 different monomers of the dimer are shaded in green and brown.
Currently fully validated human acyl-protein thioesterases are APT1[8] and APT2[9] which share 66% sequence homology.[10]
Additionally there are a handful of putative acyl-protein thioesterases reported, including the ABHD17 enzyme family.[11][12] In the lysosome, PPT1 of the palmitoyl protein thioesterase family has similar enzymatic activity as acyl-protein thioesterases.
Structure
Acyl-protein thioesterases feature 3 major structural components that determine protein function and substrate processing: 1. A conserved, classical catalytic triad to break ester and thioester bonds;[2] 2. A long hydrophobic substrate tunnel to accommodate the palmitoyl moiety, as identified in the crystal structures of human acyl-protein thioesterase 1,[2] human acyl-protein thioesterase 2[13] and Zea mays acyl-protein thioesterase 2;[14] 3. A lid-loop that covers the catalytic site, is highly flexible and is a main factor determining the enzyme's product release rate.[14]
Inhibition
The involvement in controlling the localization of the oncogeneRas has made acyl-protein thioesterases potential cancerdrug targets.[15]Inhibition of acyl-protein thioesterases is believed to increase mislocalization of Ras at the cell's membranes, eventually leading to a collapse of the Ras cycle. Inhibitors for acyl-protein thioesterases have been specifically targeting the hydrophobic substrate tunnel,[16][13] the catalytic site serine[17] or both.[18]
Research
Current approaches to study the biological activity of Acyl-protein Thioesterases include proteomics, monitoring the trafficking of microinjected fluorescent substrates,[19][7] the use of cell-permeable substrate mimetics,[20] and cell permeable small molecule fluorescent chemical tools.[21][22][23][24]
^Wang A, Yang HC, Friedman P, Johnson CA, Dennis EA (February 1999). "A specific human lysophospholipase: cDNA cloning, tissue distribution and kinetic characterization". Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids. 1437 (2): 157–69. doi:10.1016/s1388-1981(99)00012-8. PMID10064899.
^Chavda B, Arnott JA, Planey SL (September 2014). "Targeting protein palmitoylation: selective inhibitors and implications in disease". Expert Opinion on Drug Discovery. 9 (9): 1005–19. doi:10.1517/17460441.2014.933802. PMID24967607. S2CID207494086.
^Rusch M, Zimmermann TJ, Bürger M, Dekker FJ, Görmer K, Triola G, Brockmeyer A, Janning P, Böttcher T, Sieber SA, Vetter IR, Hedberg C, Waldmann H (October 2011). "Identification of acyl protein thioesterases 1 and 2 as the cellular targets of the Ras-signaling modulators palmostatin B and M". Angewandte Chemie. 50 (42): 9838–42. doi:10.1002/anie.201102967. PMID21905186.
^Zimmermann TJ, Bürger M, Tashiro E, Kondoh Y, Martinez NE, Görmer K, Rosin-Steiner S, Shimizu T, Ozaki S, Mikoshiba K, Watanabe N, Hall D, Vetter IR, Osada H, Hedberg C, Waldmann H (January 2013). "Boron-based inhibitors of acyl protein thioesterases 1 and 2". ChemBioChem. 14 (1): 115–22. doi:10.1002/cbic.201200571. PMID23239555. S2CID205557212.
^Görmer K, Bürger M, Kruijtzer JA, Vetter I, Vartak N, Brunsveld L, Bastiaens PI, Liskamp RM, Triola G, Waldmann H (May 2012). "Chemical-biological exploration of the limits of the Ras de- and repalmitoylating machinery". ChemBioChem. 13 (7): 1017–23. doi:10.1002/cbic.201200078. PMID22488913. S2CID37748152.
^Creaser SP, Peterson BR (March 2002). "Sensitive and rapid analysis of protein palmitoylation with a synthetic cell-permeable mimic of SRC oncoproteins". Journal of the American Chemical Society. 124 (11): 2444–5. doi:10.1021/ja017671x. PMID11890786.