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Thiol-disulfide organization in alliin lyase (alliinase) from garlic (Allium sativum).

ABSTRACT: Alliinase, an enzyme found in garlic, catalyzes the synthesis of the well-known chemically and therapeutically active compound allicin (diallyl thiosulfinate). The enzyme is a homodimeric glycoprotein that belongs to the fold-type I family of pyridoxal-5'-phosphate-dependent enzymes. There are 10 cysteine residues per alliinase monomer, eight of which form four disulfide bridges and two are free thiols. Cys368 and Cys376 form a S--S bridge located near the C-terminal and plays an important role in maintaining both the rigidity of the catalytic domain and the substrate-cofactor relative orientation. We demonstrated here that the chemical modification of allinase with the colored --SH reagent N-(4-dimethylamino-3,5-dinitrophenyl) maleimide yielded chromophore-bearing peptides and showed that the Cys220 and Cys350 thiol groups are accesible in solution. Moreover, electron paramagnetic resonance kinetic measurements using disulfide containing a stable nitroxyl biradical showed that the accessibilities of the two --SH groups in Cys220 and Cys350 differ. Neither enzyme activity nor protein structure (measured by circular dichroism) were affected by the chemical modification of the free thiols, indicating that alliinase activity does not require free --SH groups. This allowed the oriented conjugation of alliinase, via the --SH groups, with low- or high-molecular-weight molecules as we showed here. Modification of the alliinase thiols with biotin and their subsequent binding to immobilized streptavidin enabled the efficient enzymatic production of allicin.

SUBMITTER: Weiner L

PROVIDER: S-EPMC2708034 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature

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Thiol-disulfide organization in alliin lyase (alliinase) from garlic (Allium sativum).

Weiner Lev L Shin Irina I Shimon Linda J W LJ Miron Talia T Wilchek Meir M Mirelman David D Frolow Felix F Rabinkov Aharon A

Protein science : a publication of the Protein Society 20090101 1

Alliinase, an enzyme found in garlic, catalyzes the synthesis of the well-known chemically and therapeutically active compound allicin (diallyl thiosulfinate). The enzyme is a homodimeric glycoprotein that belongs to the fold-type I family of pyridoxal-5'-phosphate-dependent enzymes. There are 10 cysteine residues per alliinase monomer, eight of which form four disulfide bridges and two are free thiols. Cys368 and Cys376 form a S--S bridge located near the C-terminal and plays an important role ...[more]

PMID: 19177363

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Project description:BACKGROUND:Alliinase is an important enzyme occurring in Allium species that converts precursors of sulfuric compounds, cysteine sulfoxides into a biologically active substance termed allicin. Allicin facilitates garlic defense against pests and produces health-promoting compounds. Alliinase is encoded by members of a multigene family that has not yet been sufficiently characterized, namely with regard to the copy numbers occurring within the genome and the polymorphisms among the family members. RESULTS:We cloned 45 full-length alliinase amplicons of cultivar (cv.) Jovan. Sequence analyses revealed nine different sequence variants (SVs), confirming the multilocus nature of this gene family. Several mutations in exons, mainly occurring in the first exon coding for vacuolar signal peptide, were found. These results enabled us to identify sequences with putatively modified vacuole-targeting abilities. We found additional sequence variants using partial amplicons. We estimated that the minimum number of gene copies in the diploid genome of the investigated cultivar was fourteen. We obtained similar results for another three cultivars, which differed in bolting type and place of origin. The further identification of high degree of polymorphisms in the intron regions allowed us to develop a specific polymerase chain reaction assay capable to capture intron length polymorphism (ILP). This assay was used to screen 131 additional accessions. Polymorphic data were used for cluster analysis, which separated the bolting and non-bolting garlic types and those with high cysteine-sulfoxide contents in a similar way as AFLP analysis in previous study. These newly developed markers can be further applied for the selection of desirable garlic genotypes. CONCLUSIONS:Detailed analysis of sequences confirmed multigenic nature of garlic alliinase. Intron and exon polymorphism analysis generated similar results as whole genome variability assessed previously by AFLP. Detected polymorphism is thus also associated with cysteine-sulphoxide content in individual genotypes. ILP markers capable to detect intron polymorphisms were newly developed. Developed markers could be applied in garlic breeding. Higher genetic variability found in bolting genotypes may indicates longer period of their sexual propagation in comparison with nonbolting genotypes.

Dataset Information

Thiol-disulfide organization in alliin lyase (alliinase) from garlic (Allium sativum).

Publications

Thiol-disulfide organization in alliin lyase (alliinase) from garlic (Allium sativum).

Similar Datasets

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