Phosphoprotein refers to protein carrying at least one phosphorylated amino acids. Phosphorylation is regulated by the complex interplay of protein kinase and phosphatase. Phosphorylation commonly occurs on the hydroxyl groups of serine, threonine and tyrosine (O-phosphate) although also on hydroxy-proline occasionally. N-, S- and acyl-phosphorylation is less prevalent and mostly occurs on histidine, arginine and lysine (N-phosphate), cysteine (S-phosphate), aspartic and glutamic acids (acyl-phosphates) respectively1. Protein with more than one phosphorylation sites can have different biological functions depending on the pattern of phosphorylation. Phosphoamino acids have different stability in different pH environment. For example, O-phosphate is more stable in acidic and neutral milieu.