Characterization of the major proteins from Vitis vinifera seeds

Abstract

The major protein from the endosperm of Vitis vinifera cv. Chardonnay is a globulin, homogeneous by size ( M τ ⩾ 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 M r which in turn are composed of disulfide-bridged peptides, M τ 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 ( M τ = 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.