title: Cloning and expression of γ-glutamyl transpeptidase and its relationship to greening in crushed garlic (Allium sativum) cloves.
abstract: BACKGROUND
  Garlic greening occurs when garlic cloves are stored at low temperature, increasing 1-propenyl cysteine sulfoxide, which is induced by γ-glutamyl transpeptidase (GGT) activity. Although the metabolism of the γ-glutamyl peptide is important for the biosynthesis of green pigments in crushed garlic cloves, garlic GGT is poorly characterised.
  
  
  RESULTS
  For the analysis of GGT at the gene level, the garlic GGT sequence was partially cloned using an onion GGT sequence. The relationship between garlic greening and related gene expressions, depending on storage condition, was investigated using reverse transcription polymerase chain reaction for garlic GGT and alliinase. Three storage conditions were set: A, storage at a constant temperature of 20 °C; B, storage at 20 °C for 3 months and then transfer to 0 °C for an additional 3 months; C, storage at 0 °C for 3 months and then transfer to 20 °C for an additional 3 months. GGT expression increased under storage condition B and decreased under storage condition C. However, alliinase expression was not affected by storage condition.
  
  
  CONCLUSIONS
  Greening in crushed garlic cloves increases with increasing GGT expression at low temperature, while alliinase expression is not affected.
authors.affiliation: World Institute of Kimchi, Research and Development Division, 516 Baekhyun-dong, Bundang-gu, Sungnam-si, Gyeounggi-do 463-746, Korea.
authors.forename: Jungeun
authors.initials: J
authors.lastname: Cho
authors.forename: Minkyu
authors.initials: M
authors.lastname: Park
authors.forename: Doil
authors.initials: D
authors.lastname: Choi
authors.forename: Seung Koo
authors.initials: SK
authors.lastname: Lee
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular; D061353:Food Storage; D005737:Garlic / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010860:Pigments, Biological; D013886:Thiosulfonic Acids / Q000737:chemistry / Q000378:metabolism; D005723:gamma-Glutamyltransferase / Q000235:genetics / Q000378:metabolism*
chemical_list: D010860:Pigments, Biological; D013886:Thiosulfonic Acids; D005723:gamma-Glutamyltransferase