Monaghan Erin K, Venkatachalam Mahesh, Seavy Margaret, Beyer Kirsten, Sampson Hugh A, Roux Kenneth H, Sathe Shridhar K
Department of Nutrition, Food and Exercise Sciences and Department of Biological Science, Florida State University, Tallahassee, Florida 32306, USA.
J Agric Food Chem. 2008 Feb 13;56(3):765-77. doi: 10.1021/jf072079y. Epub 2008 Jan 12.
As a result of methionine deficiency, legume proteins are considered to be incomplete, and therefore there is a need to explore ways to improve legume protein amino acid balance. Using rabbit anti-soybean sulfur-rich protein (SRP) polyclonal antibodies (pAb), sensitive immunoassays (nanogram sensitivity) were developed. The immunoassays detected SRP in all soybean seeds and soybean-based commercial samples examined. In addition, the presence of pAb cross-reactive proteins was detected in certain dry beans and oilseeds. The cross-reactive proteins were isolated using purified IgG-based immunoaffinity column chromatography. Biochemical analyses including N-terminal amino acid sequencing and amino acid composition indicated that the cross-reactive proteins were comparable to soybean SRP. The cross-reactive proteins contained methionine (1.6-2.4 residues/100 residues) and cysteine (2.4-3.6 residues/100 residues), which satisfies the FAO/WHO recommended pattern for sulfur amino acids in both adults and children (2-5 years old). The results suggest the presence of constitutive SRPs in several dry beans and oilseeds.
