CHARACTERIZATION OF THE MAJOR PROTEINS FROM VITIS-VINIFERA SEEDS

The major protein from the endosperm of Vitis vinifera cv. Chardonnay is a globulin, homogeneous by size (Mτ ≥ 400 kD after PAGE) and highly heterogenous by charge, 23 bands being resolved by IEF, with pI values 4.8-5 for the major components, and up to pH 7 for the minor ones. The native structure is assembled from non-covalently bound subunits, with Mr which in turn are composed of disulfide-bridged peptides, Mτ 19-21 kD and 38-44 kD. The focusing pattern of the denatured protein includes 15 acidic (pI values = 4.25-4.8) and two alkaline (Mτ = 26 kD, pI = 6.8-6.9) components. None of the major bands contains sugar or lipid mojeties. Several enzymatic activities are detected: esterase, phosphoglucomutase, acid phosphatase, peroxydase, malic, alcohol and a little lactic dehydrogenase; no protease inhibitors can be identified. The quali-quantitative variability among proteins extracted from individual seeds amounts to approx. 10%; only large samples, including 20-30 seeds, are thus likely to be representative of the genetic set-up of a given Vitis clone.