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PhosphoSens CDK18/CycY Protein Kinase Assays, Substrates & Recombinant Enzymes
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About CDK18/CycY
CDK18 (Cyclin-Dependent Kinase 18), also known as PCTAIRE3, is a member of the PCTAIRE subfamily of cyclin-dependent kinases that associates with Cyclin Y (CycY) as its primary activating cyclin partner. Unlike canonical cell-cycle CDKs, CDK18 plays roles in DNA damage response, replication stress management, and neuronal differentiation. CDK18 phosphorylates substrates involved in ATR pathway activation and fork stability, including components that regulate replication origin firing. Dysregulation of CDK18 has been implicated in multiple cancer types, including glioblastoma, breast cancer, and prostate cancer, where altered expression correlates with chemoresistance and poor prognosis. CDK18 also participates in ciliogenesis and autophagy regulation. Because CDK18 activity modulates DNA replication fidelity and the cellular response to genotoxic stress, it represents an emerging oncology drug target, particularly in tumors relying on replication stress tolerance pathways for survival after chemotherapy or radiation.
Why PhosphoSens for CDK18/CycY?
CDK18 presents specific assay challenges: its relatively low intrinsic activity, requirement for CycY co-activation, and sensitivity to non-physiological ATP concentrations can cause endpoint assays such as ADP-Glo and HTRF to underreport activity or miss inhibitor mechanism. Radiometric methods add safety burden and lack kinetic resolution. PhosphoSens continuous fluorescence technology monitors CDK18 substrate phosphorylation in real time using physiological ATP concentrations, generating full progress curves that distinguish competitive, covalent, and slow-binding inhibitors — including accurate kinact/KI determination for irreversible compounds. Real-time readout eliminates endpoint artifacts from compound interference with luminescence or antibody binding, and reduces reagent consumption during screening. This enables robust CDK18 assay development at Km ATP, preserving pharmacological relevance for inhibitor profiling.
Key Pathways:
ATR-mediated DNA replication stress response
CDK/Cyclin cell cycle regulation
Autophagy signaling
Ciliogenesis and hedgehog signaling
Talk to a Scientist
Have questions about CDK18/CycY assay design, selectivity panels, or covalent inhibitor characterization?
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How pricing works:
Select a kit or substrate below, then request a quote. Bundle discounts apply automatically.
Select a kit or substrate below, then request a quote. Bundle discounts apply automatically.
Real-Time CDK18/CycY Activity Assays
Continuous, real-time fluorescent assays optimized for quantitative CDK18/CycY activity measurements, IC50 determination, and mechanistic studies.
Assay Format: Continuous kinetic fluorescence (real-time)
PhosphoSens-Kinetic assays directly quantify enzyme activity by continuously monitoring substrate phosphorylation or dephosphorylation in real time, generating a full progress curve in every well.
Learn more about PhosphoSens-Kinetic →Need pricing or availability? Select a kit or substrate to request a quote below.
Kits
PhosphoSens-Kinetic Kinase Activity Kit - AQT0255
Ready-to-use assay kits containing substrate and all essential reagents.
Kit Contents
- Optimized PhosphoSens® substrate (AQT0255)
- ATP, DTT, EGTA, Reaction Buffer & Dilution Buffer
Automatically save 10% when bundling 10ug recombinant enzyme with your 1,000 assay kit. View enzymes
Price: $425
Substrate
PhosphoSens Kinase Substrate AQT0255
Bulk PhosphoSens® substrate for assay development and high-throughput workflows.
Specifications
Automatically save 10% when bundling Reagent Packs with your substrate. View Reagent Packs
Price: $2795
Ready to request pricing for CDK18/CycY?
Select a kit, substrate, or enzyme above. Our team will confirm pricing, availability, and any applicable bundle discounts.
Request a QuoteTRF CDK18/CycY Screening Assays
Robust endpoint TRF assays optimized for high-throughput screening and quantitative CDK18/CycY activity measurement in plate-based workflows.
Assay Format: Time-resolved fluorescence (TRF, endpoint)
PhosphoSens-Red assays use europium-based time-resolved fluorescence detection to enable robust, plate-based quantification of enzyme activity, making them well suited for high-throughput screening workflows.
Learn more about PhosphoSens-Red →Need pricing or availability? Select a kit or substrate to request a quote below.
Kits
PhosphoSens-Red Kinase Activity Kit - AQT0730
Ready-to-use TRF assay kits containing substrate and essential reagents.
Kit Contents
- Optimized PhosphoSens® substrate (AQT0730)
- ATP, DTT, EGTA, Reaction Buffer & Dilution Buffer
- Europium Detection Solution
Automatically save 10% when bundling 10ug recombinant enzyme with your 1,000 assay kit. View enzymes
Price: $455
Substrate
PhosphoSens Kinase Substrate AQT0730
Bulk substrate for PhosphoSens-Red TRF assays and high-throughput workflows.
Specifications
Automatically save 10% when bundling Reagent Packs with your substrate. View Reagent Packs
Price: $2795
Ready to request pricing for CDK18/CycY?
Select a kit, substrate, or enzyme above. Our team will confirm pricing, availability, and any applicable bundle discounts.
Request a QuoteNo recombinant enzymes are currently available for CDK18/CycY.
Frequently Asked Questions: CDK18/CycY Assays
What substrate does AssayQuant recommend for CDK18/CycY activity assays?
AssayQuant offers PhosphoSens CSox-based peptide substrates optimized for CDK-family kinases, selected for efficient phosphorylation by the CDK18/CycY complex. These substrates are validated at physiological ATP concentrations to ensure pharmacologically relevant inhibitor IC50 measurements. Contact our scientific team for substrate recommendations specific to your CDK18 assay format.
Can PhosphoSens assays detect covalent inhibitors of CDK18?
Yes. Because PhosphoSens technology generates continuous, real-time progress curves, it is uniquely suited to capture the kinetics of covalent inhibition, enabling direct determination of kinact and KI parameters for irreversible CDK18 inhibitors. This capability is not available with endpoint methods such as ADP-Glo or HTRF, which provide only a single time-point snapshot.
How does using physiological ATP concentrations affect CDK18 inhibitor profiling?
Many CDK inhibitors are ATP-competitive, so assaying at artificially low ATP concentrations artificially inflates apparent potency and misrepresents true cellular IC50 values. PhosphoSens CDK18 assays run at or near the physiological Km for ATP, providing inhibitor potency data that more accurately predicts cellular and in vivo efficacy, reducing late-stage attrition in drug discovery campaigns.
Data & Resources
Explore data and documents to support your kinase and phosphatase experiments. Download sample data, protocols and other resources to see how our assays perform and to help you get started in your own lab. All validation data generated using PhosphoSens® assays under recommended conditions.
Sample Report: AQT0734 - EGFR Assay Validation Report
Each validation report provides experimental conditions and data showing:
- Enzyme titration and linearity
- Sensor peptide substrate titration and Km determination
- ATP titration and Km determination
- DMSO titration and assay tolerance
- Inhibitor titration and IC50 determination
Protocol
Inhibitor IC50 Protocol
See how the PhosphoSens-Kinetic Assay can be used to find the IC50 of a kinase inhibitor.
Download Protocol →Webinar
Webinar: Continuous Assay Validation
Discover how continuous assay formats power deep understanding of kinase function. See how PhosphoSens® assays guide inhibitor profiling, selectivity assessment, and mechanistic characterization.
Watch the Webinar →Service
KinSight™ CDK18/CycY Profiling
Need broader selectivity data? KinSight profiling runs your compounds across our full kinase panel under identical PhosphoSens conditions.
Learn about KinSight →Stay Informed
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