Determination of the physicochemical and functional properties of the native and recombinant coconut 11S globulin

The crude recombinant cocosin was extracted from bacterial expression host cells carrying the gene insert. The R-cocosin was found to be highly soluble at 60 percent ammonium sulfate cut. However, further generation of R-cocosin was stopped due to the incomplete DNA sequence of the gene obtained in a separate study. On the other hand, native cocosin (N-cocosin) was purified in sufficient amounts for use in the determination of its physicochemical and functional properties. This is the final report on the physicochemical and functional properties of coconut 11S globulin. The solubility of cocosin decreased at pH 3.4 to 5.4 a low ionic strength (micron = 0.08), with the minimum solubility occurring at pH 5.4. Solubility then increased with increasing pH reaching a maximum solubility of 72.3 percent observed at pH 8.2. The solubility of cocosin at different pH at high ionic strength (micron = 0.5) was relatively higher than that at low ionic strength. Cocosin was 80-100 percent soluble across pH 5.4-9.0. However, very low solubility was observed below pH 5. However, the solubility rapidly decreased below pH 5 with a minimum solubility of 10.2 percent observed at pH 3.4. Three cocosin sub units (32, 24, and 21 R KD) showed fair resistance to chymotrypsin digestion while two other subunits (55 and 35 KD) were susceptible. Densitometric analysis showed that 38 percent of subunit 32 KD remained after 60 min while 58 percent and 56 percent remained for subunits 24 and 21 KD, respectively. The amount of sulfhydry groups (SH) in cocosin was calculated to be 8.3 moles SH/mole of the protein. The most stable emulsion was observed with cocosin in 0 M Nacl. Emulsions were still visible at the bottom of the tube for cocosin in a 0 M NaCl even after 60 min standing, while creaming and separation were already evident emulsions in 0.4M NaCl after only 10 min standing. Stability of the emulsion in 0.1 M NaCl was intermediate separation was evident after 30 minutes of standing. Complete phase separation was achieved after 140 min of standing in all three treatments.