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Related Concept Videos

Phosphorylation01:02

Phosphorylation

The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
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 Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Phosphoinositides and PIPs01:42

Phosphoinositides and PIPs

Phosphoinositides are a group of phospholipids containing a glycerol backbone with two fatty acid chains and a phosphate attached to a myoinositol sugar ring. The inositol head group extends into the cytoplasm, where it is modified by adding phosphate groups to form phosphatidylinositol phosphates or PIPs.
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
Synthesis of Phosphatidylcholine in the ER Membrane01:27

Synthesis of Phosphatidylcholine in the ER Membrane

The ER synthesizes lipids for building cell membranes and performing cellular functions such as energy storage and signaling. The lipid synthesis machinery embedded in the ER membrane primarily collects all reactants from the cytosol. Following synthesis, the secretory pathway and the ER contact sites distribute these lipids to other cellular organelles. Additionally, the energy-rich triacylglycerides are transported from the ER via lipid droplets.
The major components of all eukaryotic cell...
Amplifying Signals via Enzymatic Cascade01:22

Amplifying Signals via Enzymatic Cascade

When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze the...
Transducer Mechanism: Enzyme-Linked Receptors01:27

Transducer Mechanism: Enzyme-Linked Receptors

Enzyme-linked receptors are cell-surface receptors acting as an enzyme or associating with an enzyme intracellularly. They make excellent drug targets. Drugs can bind to the extracellular ligand-binding domain or directly affect their enzymatic domain and alter their activity.
Major types that are helpful drug targets include:

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Related Experiment Video

Updated: Jul 27, 2026

Recombinant α- β- and γ-Synucleins Stimulate Protein Phosphatase 2A Catalytic Subunit Activity in Cell Free Assays
09:36

Recombinant α- β- and γ-Synucleins Stimulate Protein Phosphatase 2A Catalytic Subunit Activity in Cell Free Assays

Published on: August 13, 2017

A reinterpretation of phosphatase-N.

O O Njoku, J A Early, J R Lumb

    Oncodevelopmental Biology and Medicine : the Journal of the International Society for Oncodevelopmental Biology and Medicine
    |January 1, 1982
    PubMed
    Summary

    Murine lymphoma alkaline phosphatase (APase) hydrolyzes both p-Nitrophenyl phosphatase (pNPP) and Cysteamine-S-phosphate (CASP) substrates. This enzyme shows a preference for pNPP but also cleaves CASP at a reduced rate.

    Area of Science:

    • Biochemistry
    • Enzymology
    • Cancer Biology

    Background:

    • Alkaline phosphatase (APase) is an enzyme implicated in various biological processes, including cancer.
    • The substrate specificity of APase in murine lymphomas is not fully understood, with conflicting reports regarding its activity on specific substrates.

    Purpose of the Study:

    • To investigate and clarify the substrate specificity of alkaline phosphatase (APase) found in murine lymphomas.
    • To determine if murine lymphoma APase can hydrolyze Cysteamine-S-phosphate (CASP), a substrate with a sulfur-phosphorus bond, in addition to the standard p-Nitrophenyl phosphatase (pNPP).

    Main Methods:

    • Enzyme kinetics studies were performed using pNPP and CASP as substrates.
    • Biochemical characterization included assessing pH optimum, heat inactivation, magnesium activation, and inhibition by L-homoarginine and EDTA.

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  • Enzyme activity was monitored during partial purification stages.

    • Main Results:

    • Murine lymphoma APase consistently hydrolyzed CASP at approximately one-third the rate of pNPP hydrolysis across all tested conditions.
    • Biochemical characteristics confirmed the enzyme's activity on both substrates, indicating a preference for pNPP.
    • The findings contradict previous reports suggesting that murine lymphoma APase does not cleave CASP.

    Conclusions:

    • Murine lymphoma APase exhibits substrate preference for pNPP but is capable of hydrolyzing CASP, albeit at a lower rate.
    • The observed hydrolysis of CASP suggests the same isozyme acts on both O-P and S-P bonds.
    • Discrepancies with previous research may stem from differing interpretations of the data rather than experimental results.