A partial cDNA, isolated from an early developing pea (Pisum sativum L.) embryo library, was found to encode a plant homologue of the regulatory subunit (PR65) of protein phosphatase 2A (PP2A). Comparison of the deduced amino acid sequence with a human PR65 sequence showed that the regulatory subunit of PP2A has been highly conserved during evolution. Southern analysis demonstrated that in pea and rape the catalytic and regulatory subunits of PP2A are encoded by multigene families. The levels of the transcripts encoding each subunit are developmentally regulated during pea embryogenesis and expression of the regulatory subunit is not solely restricted to the embryo.

Several chemical methods have been tested for their suitability as screening procedures for estimation of the protein content and quality of cowpea (Vigna unguiculata) meals.Preliminaryestimates of crude protein can be obtained by the UDY dye-binding procedure, followed by the automated microKjeldah1 (% N x 6.25) method using, for example, Carlo Erba equipment. Total amino acid nitrogen was estimated also with the Carlo Erba apparatus and for the cowpea varieties examined a positive correlation between the total amino acid nitrogen and total nitrogen contents was found. Total sulphur was evaluated as a measure of the sulpho-amino acids in cowpea meals. Total sulphur was determined by wet digestion and subsequent turbidimetric estimation of barium sulphate. Methionine was determined in meal hydrolysates by a Locarte Autoanalyzer. Cysteine was determined either as cysteic acid on the Locarte Autoanalyzer or as bismuth sulphide.The results obtained for cowpea meals showed that there was a relatively small variation in the total sulphur and in the sulpho-amino acid contents. Although the relation between total sulphur and sulpho-amino acids was found to be significant at the 95 % confidence level, the confidence limits were wide and at this stage a definite recommendation cannot be given as to the probable usefulness of the total sulphur-screening procedure. A strong negative correlation was observed between both methionine and sulpho-amino acids/l6 g of N and % crude protein.Similarly, a negative relationship was observed between total sulphur/lb g of N and % crude protein.