Molecular diversity of tuliposide B-converting enzyme in tulip (Tulipa gesneriana): identification of the third isozyme with a distinct expression profile

• Published in: Bioscience, biotechnology, and biochemistry biotechnology, and biochemistry, 2018-05, Vol.82 (5), p.810-820
• Main Authors: Nomura, Taiji, Kuchida, Ryo, Kitaoka, Naoki, Kato, Yasuo
• Format: Article
• Language: English
• ISSN: 0916-8451; 1347-6947
• DOI: 10.1080/09168451.2018.1438170

Abstract 6-Tuliposide B (PosB), a major secondary metabolite that accumulates in tulip (Tulipa gesneriana), is converted to the antibacterial lactone, tulipalin B (PaB), by PosB-converting enzyme (TCEB). TgTCEB1 and TgTCEB-R, which encode TCEB, are specifically expressed in tulip pollen and roots, respectively, but are hardly expressed in other tissues (e.g. leaves) despite the presence of substantial PosB-converting activity, suggesting the existence of another TCEB isozyme. Here, we describe the identification of TgTCEB-L (“L” for leaf), a paralog of TgTCEB1 and TgTCEB-R, from leaves via native enzyme purification. The enzymatic characters of TgTCEB-L, including catalytic activity and subcellular localization, were substantially the same as those of TgTCEB1 and TgTCEB-R. However, TgTCEB-L did not exhibit tissue-specific expression. Identification of TgTCEB-L explains the PosB-converting activity detected in tissues where TgTCEB1 and TgTCEB-R transcripts could not be detected, indicating that tulip subtilizes the three TgTCEB isozymes depending on the tissue. Three isozymes are involved in the conversion of 6-tuliposide B, a major secondary metabolite in tulip, to antibacterial tulipalin B.