PNL Volume 14

1982

RESEARCH REPORTS

QUANTITATIVE EXTRACTION OF REMAINING AMOUNTS OF SOLUBLE PROTEINS

FROM PEA SEEDS UNDER ALKALINE CONDITIONS

Gerhards, E. Institute of Genetics, University of Bonn

Federal Republic of Germany

The extractable proteins of the garden pea are separated according

to their solubility into two classes, the water soluble albumins and the

salt soluble globulins. To extract proteins completely, pulverized

seeds are treated with salt solution (NaCl) buffered with phosphate

(pH 7). However, even after repeated extractions, the residue still

contains some seed protein. Therefore, after extracting in salt solu-

tions, the seed flour was treated under alkaline conditions

(0.04 m NaOH) with small amounts (0.5%) of sodium dodecyl sulfate (SDS).

By this method additional soluble protein could be extracted from the

seeds.

The polypeptide composition of the seed proteins was determined by

SDS-Polyacrylamide-Gel-Electrophoresis (PAGE). The banding pattern of

the alkaline extract was compared with the polypeptides of the albumins

and globulins from var. 'Dippes Gelbe Viktoria' and mutant 1000 of

Gottschalk's collection. As shown in the pherogram, the albumin frac-

tions (Fig. 1a) of both genotypes differed distinctly from the globulin

fractions (Fig. 1b) and the alkaline fractions (Fig. 1c). However, the

globulins were similar to the alkaline-extracted proteins. Only two

small polypeptides In the alkaline fraction were lacking, as indicated

in Fig. 1. Thus, the third alkaline-extracted fraction did not repre-

sent an independent protein fraction. It seems to be a contradiction

to the classification of seed proteins because all types of globulin are

regarded as being soluble in salt solutions. However, the finding is in

agreement with the fact that the proteins of Pisum sativum could be sub-

divided exclusively in albumins and globulins. Nevertheless, this

method allows one to extract additional amounts of globulins from

ripened seeds not extractable under conditions mentioned above.



PNL Volume 14	1982	RESEARCH REPORTS 11



Fig. 1. Polypeptide composition of albumin fraction (a), globulin frac- tion (b), and the alkaline extracted proteins (c) of the initial line and mutant 1000 compared with a marker set. Arrows indicate deviations in banding pattern of the alkaline fractions. kD = molecular weight in kilo Daltons