title: The plant invertase inhibitor shares structural properties and disulfide bridges arrangement with the pectin methylesterase inhibitor.
abstract: Attempts to purify the inhibitor of pectin methylesterase (PMEI) from the soluble extract of ripe apricot (Prunus armeniaca) fruit led to isolation of a protein (Pa-INH) similar to PMEI, but having invertase inhibitory activity against vacuolar invertase from tomato. The molecular charge, the native and SDS-PAGE molecular weights were similar to those of PMEI. Partial amino acid sequence indicated a high level of identity with invertase inhibitors and a significant identity with PMEI. Circular dichroism analysis showed a mainly alpha-helix secondary structure for both the inhibitors and a higher thermostability of Pa-INH. Four Cys residues forming disulfide bridges in PMEI were conserved in Pa-INH. Similarly to PMEI, these residues were linked by disulfide bridges (first to second and third to fourth). The free Cys139 of PMEI is substituted by Ala in Pa-INH. The results reported in this study suggest a common structural arrangement of the two inhibitors.
mesh_terms: D000595:Amino Acid Sequence; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004220:Disulfides / Q000737:chemistry*; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D005638:Fruit / Q000737:chemistry; D018551:Solanum lycopersicum / Q000737:chemistry*; D008969:Molecular Sequence Data; D027861:Prunus / Q000737:chemistry*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D013696:Temperature; D014357:Trypsin / Q000378:metabolism; D043324:beta-Fructofuranosidase / Q000037:antagonists & inhibitors*
chemical_list: D004220:Disulfides; D004791:Enzyme Inhibitors; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D043324:beta-Fructofuranosidase; D014357:Trypsin