Three forms of enolase separated by counter-current distribution

Studies of protein-protein interaction using countercurrent distribution in aqueous two-phase systems. Partition behaviour of six Calvin-cycle enzymes from a crude spinach (Spinacia oleracea) chloroplast extract

The partition behaviour of six enzymes of the Calvin cycle in extracts of chloroplasts from spinach (Spinacia oleracea) between two aqueous phases has been studied by countercurrent distribution. The enzymes showed distribution patterns which indicate heterogeneity and the presence of two or three fractions of most of the enzymes. When two of the enzymes, phosphoglycerate kinase and fructose-bisphosphate aldolase, were partitioned in both purified and partially purified form, they behaved like homogeneous substances. These results indicate that countercurrent distribution of crude extracts in aqueous two-phase systems is a useful method to study protein-protein interaction.

Enhanced discrimination in the partition of proteins by aqueous polymer two-phase systems

Aqueous polymer two-phase systems containing dextran T-500 and PEG 4000 can be prepared which are biphasic below 18 degrees C and monophasic at higher temperatures. Both liganded and unliganded forms of glutamate dehydrogenase and troponin, which have similar partition coefficients if the protein is added to a two-phase system at 4 degrees C, have widely differing partition coefficients if added to the same system in the monophasic state at 20 degrees C and subsequently cooled to 4 degrees C.

Cross partition and determination of net charge of the isoenzymes of enolase

Enolase from bakers' yeast was separated into three isoenzymes by countercurrent distribution. The isoenzymes were partitioned in aqueous polymer two-phase systems containing positively charged trimethylamino poly(ethylene glycol) or negatively charged poly(ethylene glycol) sulphonate. The plots of the partition coefficient of each isoenzyme versus pH in the two biphasic systems intersect at pH equal to the isoelectric point. From slopes of the plots, the net charge of the isoenzymes at pH 6.57 was determined to be +2, -3, and -8 respectively.