M. Aoubala et al., TRYPTIC CLEAVAGE OF GASTRIC LIPASES - LOCATION OF THE SINGLE DISULFIDE BRIDGE, Biochimica et biophysica acta, L. Lipids and lipid metabolism, 1213(3), 1994, pp. 319-324
Human (HGL) and rabbit (RGL) gastric lipases were cleaved by trypsin a
nd the resulting peptides were characterized. Exposure of HGL to tryps
in led to the production of three identified fragments (H1, H2 and H3)
resulting from cleavage sites at Lys-4 and Arg-229. Fragments H2 (Lys
-4-Arg-229) and H3 (Glu-230-Lys-379) were derived from fragment H1 (Ly
s-4-Lys-379). The single disulfide bridge (Cys-236-Cys-244) of the mol
ecule is localized in fragment H3. Out of the three cysteine residues
conserved in all known gastric lipases, the free sulfhydryl group (Cys
-227) was localized in fragment H2. Immunoblots, carried out with the
tryptic fragments of HGL and anti-HGL mAbs, revealed that five inhibit
ory mAbs immunoreacted selectively with the N-terminal fragment H2, wh
ereas two other non inhibitory mAbs immunoreacted exclusively with the
C-terminal fragment H3. Trypsin also cleaved RGL at two sites (Arg-55
and Arg-229) leading to four identifiable fragments (R1, R2, R3 and R
4). One cleavage site (Arg-229) was found to be identical in both RGL
and HGL. We propose that this latter site is localized between the two
domains of native gastric lipases.