Phosphorylation is the main form of reversible covalent modification of proteins for their regulation. This is catalyzed by a large family of enzymes called protein kinases. The dephosphorylation of phosphoproteins is carried out by another group of enzymes called protein phosphatases. The study of these enzymes and their phosphoprotein targets (also known as substrates) is having an enormous impact on our understanding of how cells are controlled and human health care delivery.

Phosphopeptides are essential tools for the study of phosphorylation process, serving as model substrates for phosphatases, as antigens for the production of antibodies against phosphorylated proteins, and as reference compounds for determining their physical parameters. The development of methods for the production of phosphopeptides has consequently attracted considerable interest over the last few years, and these endeavours have yielded reliable procedures which have now made their synthesis routine.

However, during the synthesis of phosphopeptides, the presence of phosphoamino acids cannot only make the coupling reaction sluggish but also induce the ease of assembling peptide chains, leading to a significant decrease of coupling efficiency. Consequently, the purity of crude product and the purification yield will be dramatically lowered, and in some serious cases complete reaction failure will result. After optimization of synthesis conditions when incorporating phosphoamino acids as well as consecutive amino acids, we successfully prepared peptides containing as many as six phosphorylation sites with the building block approach.

We offer phosphorylation on pSer, pTyr, pThr or D-pSer, D-pTyr, D-pThr. Phosphorylation can be in two sites, three sites, four sites and five sites.