Threonic acid is probably derived from glycated proteins or from the degradation of ascorbic acid. It is a normal component is aqeous humour and blood. Threonic acid is a substrate of L-threonate 3-dehydrogenase in ascorbate and aldarate metabolism pathway.

Phosphorylase Kinase β-Subunit Fragment (420-436) is the β-Subunit fragment (peptide 430-436) of phosphorylase kinase. Phosphorylase kinase is a serine/threonine-specific protein kinase which activates glycogen phosphorylase to release glucose-1-phosphate from glycogen.

Ac-Leu-Lys-Phe-Ser-Lys-Lys-Phe-OH