Influence of plant age on fructan content and fructosyltranserase activity in agave atrovirens karw leaves

An evaluation of non-structural carbohydrate content, fructan:fructan 1-fructosyltransferase (1-FFT; EC. 2.4.1.100) enzymatic activity and electrophoretic pattern of proteins in Agave atrovirens leaves was performed to establish the optimum age for plant harvest. The highest soluble carbohydrate content was observed in 3-year-old leaves, but inulin-type fructan content was highest in 6-year-old leaves. Fructan synthesis in A. atrovirens apparently occurs in two sequential reactions; 1-kestose is generated in the first reaction, and inulin-type fructans with degree of polymerization (DP)≥30 are obtained in the second reaction. The 1-FFT enzymatic activity was higher in 6-year-old leaves, coinciding with higher content inulin-type fructans with DP≥29 at this age. This behavior suggests a relationship between 1-FFT enzymatic activity and the concentration of fructans. A monomer was obtained in the 6-year-old leaves (MW ~70 kDa), while in the 3- and 9-year-old leaves, this monomer was associated with three subunits (MW ~50, 17 and 15 kDa) or two subunits (MW ~25 and 17 kDa), respectively. In conclusion, leaf age is a determining factor in the 1-FFT enzymatic activity, which is related to the inulin-type fructans concentration.