| Abstract
| - A full-length complementary DNA (cDNA) clone encoding aputative 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase) from papaya was amplified bypolymerase chain reactiontechnique from cDNAs synthesized from messenger RNA. Nucleotidesequence analysis of this cDNAclone revealed that it comprised a complete open reading frame codingfor 310 amino acid residues.The deduced amino acid sequence showed high identity (72−80%)with the sequence of ACC oxidasefrom other plant species. No transit peptide was found. The12 residues (P-5, A-27, G-32, H-39,H-177, D-179, L-195, Q-196, G-218, H-234, R-244, and S-246) areconserved as they are among allenzymes that require ferrous ion and ascorbate for activity. Thesesuggest that the papaya cDNAclone encodes a cytosolic ACC oxidase. Furthermore, the codingregion of ACC oxidase cDNA frompapaya was introduced into an expression vector, pET-20b(+), andtransformed into Escherichiacoli BL21(DE3). A 0.45 mL enzyme crude extract from 5 mLculture in a typical assay produced 42ppm of ethylene. A 38 kDa ACC oxidase protein was detected as thedistinctive protein by Coomassieblue staining of SDS−PAGE, and western blot immunoanalysis confirmedthe results of Coomassieblue staining. These indicate that this ACC oxidase cDNA clone canexpress active ACC oxidaseenzyme in the E. coli system. Keywords: 1-Aminocyclopropane-1-carboxylate oxidase; ACC oxidase; papaya(Carica papaya L.cv. Tainong 2)
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