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Titolo:
Aminotransferase activity and bioinformatic analysis of 1-aminocyclopropane-1-carboxylate synthase
Autore:
Feng, L; Geck, MK; Eliot, AC; Kirsch, JF;
Indirizzi:
Univ Calif Berkeley, Dept Mol & Cell Biol, Berkeley, CA 94720 USA Univ Calif Berkeley Berkeley CA USA 94720 ll Biol, Berkeley, CA 94720 USA
Titolo Testata:
BIOCHEMISTRY
fascicolo: 49, volume: 39, anno: 2000,
pagine: 15242 - 15249
SICI:
0006-2960(200012)39:49<15242:AAABAO>2.0.ZU;2-O
Fonte:
ISI
Lingua:
ENG
Soggetto:
COLI ASPARTATE-AMINOTRANSFERASE; SITE-DIRECTED MUTAGENESIS; ESCHERICHIA-COLI; ETHYLENE BIOSYNTHESIS; SUBSTRATE-SPECIFICITY; 8-AMINO-7-OXONONANOATE SYNTHASE; EVOLUTIONARY RELATIONSHIPS; CRYSTAL-STRUCTURE; MUTANT FORMS; AMINO-ACIDS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
45
Recensione:
Indirizzi per estratti:
Indirizzo: Kirsch, JF Univ Calif Berkeley, Dept Mol & Cell Biol, 229 Stanley Hall, Berkeley, CA 94720 USA Univ Calif Berkeley 229 Stanley Hall Berkeley CA USA 94720 USA
Citazione:
L. Feng et al., "Aminotransferase activity and bioinformatic analysis of 1-aminocyclopropane-1-carboxylate synthase", BIOCHEM, 39(49), 2000, pp. 15242-15249

Abstract

The mechanistic fate of pyridoxal phosphate (PLP)-dependent enzymes diverges after the quinonoid intermediate. 1-Aminocyclopropane-1-carboxylate (ACC) synthase, a member of the alpha family of PLP-dependent enzymes, is optimized to direct electrons from the quinonoid intermediate to the gamma -carbon of its substrate, S-adenosyl-L-methionine (SAM), to yield ACC and 5'-methylthioadenosine. The data presented show that this quinonoid may also accept a proton at C-4' of the cofactor to yield alpha -keto acids and the pyridoxamine phosphate (PMP) form of the enzyme when other amino acids are presented as alternative substrates. Addition of excess pyruvate converts the PMP form of the enzyme back to the PLP form. C-alpha-deprotonation from L-Ala is shown by NMR-monitored solvent exchange to be reversible with a rate that is less than 25-fold slower than that of deprotonation of SAM. The rate-determining step for transamination follows the formation of the quinonoidintermediate. The rate-determining step for alpha,gamma -elimination from enzyme-bound SAM is likewise shown to occur after C-alpha-deprotonation, and the quinonoid intermediate accumulates during this reaction. BLAST searches, sequence alignments, and structural comparisons indicate that ACC synthases are evolutionarily related to the aminotransferases. In agreement withpreviously published reports, an absence of homology was found between thealpha and beta families of the PLP-dependent enzyme superfamily.

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Documento generato il 18/09/20 alle ore 16:06:27