Reasons for choosing our testing services
ZHONGXI Testing has obtained inspection qualification certifications from multiple countries and regions worldwide. We possess a senior testing team and advanced testing methods, providing independent, impartial, and professional third-party verification services for global carbon projects.
Internationally recognized authority
Certified by multiple international standards such as CNAS, VCS, and GS, with reports universally applicable worldwide.
Global service capability
Covering 140+ countries and regions, it supports on-site detection and remote verification in multiple languages.
Professional experimental methods
Adopt standard experimental methods to ensure accurate and reliable data.
Enzyme Activity Assay Services: Quantifying Catalytic Function for Research, Bioprocessing & Diagnostics
As an independent third-party analytical service provider, we offer comprehensive enzyme activity testing for industrial enzymes, pharmaceutical targets, diagnostic markers, food processing aids, and research samples. Enzymes are biological catalysts that drive virtually every metabolic and industrial process – from proteases in detergents to polymerases in PCR, from amylases in brewing to kinases in drug discovery. Reliable measurement of enzyme activity (units per milligram, kcat, specific activity, residual activity) is essential for quality control, formulation development, mechanism studies, and regulatory compliance. Our accredited laboratory follows internationally recognised pharmacopoeial, ISO, and industry‑specific methods (USP, EP, JP, ISO 17512, ICH, AOAC) using spectrophotometry, fluorometry, chromatography, and electrochemical detection. This article outlines our enzyme activity testing capabilities – including scope, key test items, and standard test methods – to help manufacturers, biotech companies, and research laboratories validate enzymatic performance.
1. Our Testing Scope for Enzyme Activity
We cover a broad spectrum of enzyme classes, sample matrices, and reaction conditions:
By enzyme class: Hydrolases (proteases, amylases, lipases, cellulases, lactases, ureases); Oxidoreductases (laccase, peroxidase, catalase, glucose oxidase, alcohol dehydrogenase); Transferases (kinases, transaminases, glycosyltransferases); Lyases (pectate lyase, aldolase); Isomerases (glucose isomerase); Ligases (DNA ligase).
By sample matrix: Purified enzyme solutions; Crude cell lysates (bacterial, yeast, mammalian); Fermentation broths; Food ingredients (baking enzymes, juice processing enzymes); Detergent formulations (protease, lipase, amylase); Diagnostic reagents (e.g., glucose oxidase, cholesterol esterase); Pharmaceutical enzyme preparations (e.g., pancreatin, trypsin); Environmental samples (soil, water – for specific enzyme activities).
By assay type: Endpoint (single time point measurement); Kinetic (continuous monitoring of substrate depletion or product formation); Stopped‑flow / rapid quench (for fast reactions).
By detection principle: Spectrophotometric (UV‑Vis absorbance); Fluorometric (fluorescence increase/quenching); Chemiluminescent; Chromatographic (HPLC separation of substrate/product); Electrochemical (amperometric).
2. Key Test Items & Measurements We Perform
Our enzyme activity testing services quantify catalytic parameters under defined conditions. Typical deliverables include activity in international units (U), specific activity (U/mg protein), and/or kinetic constants (Km, Vmax, kcat).
2.1 Specific Activity & Total Activity
Enzyme activity (U/mL or U/g) – one unit (U) is defined as the amount of enzyme that converts 1 micromole of substrate per minute under specified conditions (temperature, pH, buffer).
Specific activity (U/mg protein) – activity normalised to total protein concentration (Bradford, BCA, or Lowry method).
Residual activity (%) – after stress treatment (heat, pH, storage), relative to initial activity.
2.2 Kinetic Parameters (Michaelis‑Menten)
Km (Michaelis constant – mM) – substrate concentration at half Vmax, indicating enzyme affinity for substrate.
Vmax (maximum reaction velocity – μmol/min) – extrapolated at saturating substrate.
kcat (turnover number – s⁻¹) – number of substrate molecules converted per active site per second.
kcat / Km (catalytic efficiency – M⁻¹·s⁻¹) – overall performance index.
2.3 Enzyme Inhibition / Activation Studies
IC50 (concentration causing 50% inhibition) – for inhibitor screening.
Inhibition constant (Ki) – competitive, uncompetitive, or mixed inhibition type.
Activation fold – increase in activity by an activator (e.g., metal ions, cofactors).
Thermal stability (T50 or half‑life at elevated temperature).
pH stability profile – residual activity after incubation at different pH values.
Storage stability (accelerated or real‑time) – activity loss over weeks/months.
Compatibility with excipients, detergents, or preservatives.
3. Standard Test Methods & Assay Protocols We Apply
All assays are performed according to industry‑standard or custom‑validated protocols. Our laboratory is ISO/IEC 17025 accredited and equipped with multi‑mode plate readers (absorbance, fluorescence, luminescence), HPLC systems, spectrophotometers, and thermal cyclers (for activity assays requiring temperature control).
3.1 Hydrolases (Protease, Amylase, Lipase, Cellulase)
Protease activity (USP <785>, ISO 14921) – casein digestion method (Folin‑Ciocalteu reagent) or azocasein (absorbance at 340 nm).
Amylase activity (INFOGEST, AOAC 935.29) – starch‑iodine colour reduction or DNS (dinitrosalicylic acid) reducing sugar method.
Lipase activity (ISO 13082, USP <781>) – titration of liberated fatty acids (pH‑stat) or p‑nitrophenyl palmitate (pNPP) colorimetric assay.
Cellulase activity (IUPAC, ISO 15928) – filter paper assay (FPase) and endoglucanase (CMC) reducing sugar method (DNS).
3.2 Oxidoreductases (Oxidase, Peroxidase, Catalase)
Glucose oxidase (GOx) activity – coupled assay with horseradish peroxidase (HRP) and ABTS or o‑dianisidine (spectrophotometric at 405 nm / 500 nm).
Lactate dehydrogenase (LDH) activity – NADH oxidation measured at 340 nm (decrease in absorbance) – ISO 19004.
Catalase activity – decomposition of H₂O₂ measured by decrease in absorbance at 240 nm (extinction coefficient 43.6 M⁻¹·cm⁻¹).
Peroxidase activity – oxidation of guaiacol (A470) or ABTS (A405).
3.3 Transferases & Kinases
Kinase activity (e.g., protein kinase A, MAPK) – coupled assay with pyruvate kinase/lactate dehydrogenase (PEP‑LDH) monitoring NADH oxidation (A340).
Transaminase (ALT, AST) activity – IFCC primary reference procedures (UV‑kinetic at 340 nm).
3.4 Pharmaceutically Relevant Enzymes
Pancreatin (USP <321>) – protease, amylase, and lipase activities assayed by USP methods.
Trypsin (USP <155>) – benzoyl‑arginine ethyl ester (BAEE) substrate (A253).
Hyaluronidase (USP <209>) – turbidity reduction (serum albumin complex).
3.5 Environmental & Food Enzymes
Laccase activity – oxidation of ABTS (A420) or syringaldazine (A530).
Pectinase (polygalacturonase) – reducing sugar method (DNS) with polygalacturonic acid.
Glutathione S‑transferase (GST) – conjugation of 1‑chloro‑2,4‑dinitrobenzene (CDNB) with glutathione (A340).
4. Why Choose Our Third‑Party Enzyme Activity Testing Services?
As an independent laboratory, we provide unbiased, accurate, and regulatory‑ready enzyme activity data. Our advantages include:
ISO/IEC 17025 accreditation – CNAS/CMA certified, with regular participation in proficiency testing (e.g., AOAC, USP reference standards).
Wide temperature & pH control – kinetic assays from 4°C to 60°C, pH 2‑12.
Low detection limits – fluorometric assays down to sub‑microUnit per mL.
Fast turnaround – routine enzyme activity (single target) in 3‑5 business days; kinetic profiling (Km, Vmax) in 7‑10 business days.
Detailed reporting – raw data, standard curves, progress curves, calculated activity (U/mL), specific activity, and statistical uncertainty (SD, CV).
Confidentiality – full protection of your enzyme sequence, formulation, and intended use.
Consultative support – our biochemists help select the most appropriate substrate, buffer, and assay format (continuous vs. endpoint) for your enzyme type.
Whether you need to release a batch of industrial protease, validate a kinase inhibitor, characterise a new amylase variant, or test pancreatin for pharmaceutical use, our enzyme activity testing experts are ready to deliver precise and reliable data.
Get Started with Your Enzyme Activity Testing Project
Contact our team with your enzyme name (EC number if known), sample type (purified, crude, formulation), substrate preference (if available), and required parameters (specific activity, Km, stability). We will provide a detailed quotation, sample submission guidelines (including recommended storage buffer), and a testing schedule. Let us help you quantify catalytic function with confidence.
This article provides an overview of our enzyme activity testing capabilities. For specific assays, sample volume, and pricing, please request a tailored service proposal.