| Citation | Philip Cohen has made outstanding contributions to the understanding of the role of protein phosphorylation and dephosphorylation in the hormonal and neural control of cellular processes. In particular he has determined the subunit structure of phosphorylase kinase and was the first, in collaboration with T C Vanaman, to report the identity of calmodulin with the delta subunit. He first reported and described in detail multiple-site phosphorylation of phosphorylase kinase and glycogen synthetase as regulatory processes in glycogen metabolism. His work on the nature and the mechanism of regulation of activity of the protein phosphatases involved in glycogen metabolism has thrown new light on this complex field, lead to a classification of protein phosphatases and to a general appraisal of their role in the regulation of a number of enzyme systems. More recently he has shown that the activity of the aminoacyl-t RNA synthetase complex is also regulated by a phosphorylation-dephosphorylation cycle. |