FRACTIONATION AND PARTIAL CHARACTERIZATION OF TEPARY BEAN (PHASEOLUS-ACUTIFOLIUS) PROTEINS

Tepary bean (Phaseolus acutifolius) proteins were fractionated sequent ially according to solubility in sodium phosphate buffer (SPB), sodium chloride (salt), ethanol, 2-mercaptoethanol (2-ME), and sodium dodecy l sulfate (SDS) solutions, and characterized. The SPB protein fraction was significantly (P < 0.05) the highest (83.2% of the recovered prot ein) followed by salt protein fraction (13.7%), 2-ME (1.5%), ethanol ( 0.8%), and SDS (0.8%) protein fractions. The amino acid compositions o f SPB, salt, ethanol, and 2-ME protein fractions were not significantl y different. Methionine and cysteine concentrations were low in all fr actions. The ethanol protein fraction had a significantly (P < 0.05) h igher cysteine content (1.5%) than 2-ME (0.95%), salt (0.2%) or SPB (t race) protein fractions. SDS-PAGE of SPB and salt protein fractions co ntained 37 and 27 polypeptides, respectively, with major bands at 29, 45, and 49 kDa. Ethanol and SDS protein fractions had only a limited n umber of small polypeptides.