Studies on the low molecular weight proteins of poppy seed (Papaver somniferum L.)

Low mol. wt. proteins of defatted poppy seed meal were separated from the high mol. wt. fraction (10S) by chromatography on Sepharose 6B. Gel electrophoresis showed that the proteins were heterogeneous and consisted of at least 5 protein fractions. In sedimentation velocity experiments a single diffuse peak was observed with S20,w value of 0.8S. The proteins contained 3.1% carbohydrate and no phosphorus. The amino acid composition of low mol. wt. proteins was different from that of the 10S protein in having higher amounts of cysteine, glutamic acid, and arginine and lower amounts of aspartic acid, leucine, isoleucine, valine, histidine, tryptophan, and phenylalanine. The mol. wt. of the proteins determined by gel filtration technique was 14 500. The low mol. wt. proteins had higher helical content (35%), unlike the 10S protein which had very little helix (5%). Attempts to isolate the monogeneous fractions by DEAE- or CM-Sephadex chromatography did not succeed.