Carnein, a Serine Protease from Noxious Plant Weed Ipomoea carnea (Morning Glory)

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• 作者：Ashok Kumar Patel ; Vijay Kumar Singh ; Medicherla V. Jagannadham
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2007
• 出版时间：July 11, 2007
• 年：2007
• 卷：55
• 期：14
• 页码：5809 - 5818
• 全文大小：448K
• 年卷期：v.55,no.14(July 11, 2007)
• ISSN：1520-5118

文摘

A new serine protease from the latex of Ipomoea carnea spp. fistulosa (Morning glory), belonging tothe Convolvulaceae family, was purified to homogeneity by ammonium sulfate fractionation followedby cation exchange chromatography. The enzyme, named carnein, has a molecular mass of 80.24kDa (matrix-assisted laser desorption/ionization time-of-flight) and an isoelectric point of pH 5.6. ThepH and temperature optima for proteolytic activity were 6.5 and 65 C, respectively. The extinctioncoefficient (₂₈₀^1%) of the enzyme was estimated as 37.12, and the protein molecule consists of 35tryptophan, 76 tyrosine, and seven cysteine residues. The effect of several inhibitors such as iodoaceticacid, diisopropylfluorophosphate, phenyl-methanesulfonyl fluoride, chymostatin, soybean trypsininhibitor, HgCl₂, 3S-3-(N-{(S)-1-[N-(4-guanidinobutyl)carbamoyl]3-ethylbutyl}carbamoyl)oxirane-2-carboxylic acid, N-ethyl maleimide, ethylene glycol-bis(-amino ethyl ether)tetraacetic acid, ethylenediamminetetraacetic acid, and o-phenonthroline indicates that carnein belongs to the family ofserine proteases. The enzyme is not prone to autolysis even at very low concentrations. The N-terminalsequence of carnein (T-T-H-S-P-E-F-L-G-L-A-E-S-S-G-L-X-P-N-S) exhibited considerable similarityto those of other plant serine proteases; the highest similarity was with alnus AG12, one of the subtilasefamily endopepetidases.