Related Experiment Video
Updated: Aug 16, 2026

A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
Published on: April 29, 2022
Temporal variations in protein tyrosine phosphatase activity during cell proliferation and differentiation
J L Calvert-Evers1, K D Hammond
1Department of Molecular Medicine and Haematology, Medical School, University of the Witwatersrand, 7 York Road, Johannesburg, Parktown, 2193, South Africa. jce@twrinet.twr.ac.za
Abstract:
Cellular oscillations in total extractable protein content and protein tyrosine phosphatase activity were analysed in proliferating and differentiating human acute promyelocytic leukaemic (HL-60) cell extracts. Differentiation was induced along the granulocytic pathway using all-trans retinoic acid (ATRA). High frequency rhythms with distinct, well defined waveforms of varying amplitude were observed for both the total protein content and for the enzyme activity of protein tyrosine phosphatase (PTP). Linear correlation analysis showed that there was no obvious relationship between the protein content and the corresponding PTP activity, suggesting that the periodic variations between these two components are relatively independent of each other. ATRA significantly altered the characteristics of the rhythms with respect to the period and amplitude and had a dampening effect on the oscillatory pattern of PTP activity. Modulation of such characteristics may be of significance with respect to the regulation of the differentiation processes and the possible reversal of transformation.
Related Concept Videos
Phosphorylation
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein.
Inhibition of Cdk Activity
Abnormal Proliferation
PI3K/mTOR/AKT Signaling Pathway

