| Catalog | Product Name | EC No. | CAS No. | Source | Price |
|---|---|---|---|---|---|
| DIA-182 | Native Microorganism N-Acetylneuraminic acid aldolase | EC 4.1.3.3 | 9027-60-5 | Microorganism | Inquiry |
| DIA-207 | Native Microorganism D-lactate dehydrogenase | EC 1.1.1.27 | 9001-60-9 | Microorganism | Inquiry |
| DIA-604 | Alpha 2, 3/6-Sialidase (BiNanH2) | EC 3.2.1.18 | 32-1-184 | Inquiry | |
| DIA-605 | Alpha 2, 3/6/8 -Sialidase (SpNanA) | EC 3.2.1.18 | 32-1-185 | Inquiry | |
| DIA-606 | Alpha 2, 6 -Sialidase (Ps26PSia) | EC 3.2.1.18 | 32-1-186 | Inquiry | |
| DIA-854 | Sialic Acid Aldolase (CgNal) | EC 4.1.3.3 | 41-3-34 | Inquiry | |
| DIA-855 | Sialic Acid Aldolase (EcNPL) | EC 4.1.3.3 | 41-3-39 | Inquiry | |
| DIA-856 | Sialidase Isoenzyme M2 (Ganglioside Sialidase) (AuSialidase M2) | EC 3.2.1.18 | 32-1-183 | Inquiry | |
| DIA-857 | Sialidase Isoenzyme S (Ganglioside Sialidase) (AuSialidase S) | EC 3.2.1.18 | 32-1-182 | Inquiry |
Sialic acids are a structurally diverse family of nine-carbon acidic monosaccharides found at the terminal positions of many glycoproteins, glycolipids, and oligosaccharides. N-Acetylneuraminic acid (Neu5Ac or NANA) is one of the most common sialic acid forms and is frequently used as the target or reference analyte in enzymatic sialic acid assays.
The enzyme requirements depend on what the assay is intended to measure. Free Neu5Ac can enter a quantitative reaction directly, whereas glycoprotein- or glycolipid-bound sialic acid must first be released. Assays designed to distinguish α2,3-, α2,6-, α2,8-, or ganglioside-associated sialylation require sialidases with an appropriate linkage and substrate preference.
Creative Enzymes supplies broad-spectrum, linkage-selective, and ganglioside-active sialidases together with sialic acid aldolases and lactate dehydrogenase for sialic acid release, quantification, glycan analysis, and assay reagent development.
Figure 1. Structures and predominant types of sialic acids. (Samraj et al., 2014)
A sialic acid assay should be defined by both its chemical target and its sample-preparation strategy. Measuring free Neu5Ac, total releasable sialic acid, and a specific sialyl linkage are different analytical objectives and may require different enzyme combinations.
Free sialic acid is already available for downstream conversion and may be measured using sialic acid aldolase followed by a pyruvate-dependent detection reaction.
Bound sialic acid is attached to glycoproteins, glycolipids, gangliosides, or oligosaccharides. It must be released before quantification if the assay is intended to determine total enzymatically releasable sialic acid.
Before selecting an enzyme, define whether the assay measures:
The analytical result should not be described as “total sialic acid” unless the release procedure has been shown to recover the relevant bound forms in the intended sample.
One enzymatic quantification strategy uses N-acetylneuraminic acid aldolase, also called N-acetylneuraminate lyase or NANA aldolase, to cleave Neu5Ac into N-acetyl-D-mannosamine and pyruvate.
The reaction sequence can be summarized as follows:
For free Neu5Ac measurement, the sialidase step may be omitted. For bound sialic acid, release efficiency becomes part of the overall analytical recovery.
Figure 2. Enzymatic assays for the identification and quantification of sialic acids. (Adapted from Cheeseman et al., 2021)
The most important design decision is not simply which sialidase has the highest activity, but which sialic acid population the assay is expected to release and measure.
| Analytical Target | Suggested Enzyme Strategy | What the Result Represents | Primary Limitation to Evaluate |
|---|---|---|---|
| Free Neu5Ac | Sialic acid aldolase followed by a compatible LDH-coupled reaction | Neu5Ac already present in an unbound or accessible form | Matrix background and specificity of the downstream reaction |
| Total enzymatically releasable sialic acid | Broad-spectrum sialidase followed by aldolase–LDH quantification | Sialic acid released from substrates accessible to the selected sialidase | Incomplete release from resistant linkages or complex glycoconjugates |
| α2,6-linked sialic acid | α2,6-selective sialidase followed by quantitative or comparative detection | Sialic acid accessible through the selected α2,6 cleavage reaction | Cross-reactivity with other linkages and substrate-context effects |
| Broad α2,3/α2,6/α2,8 coverage | Multi-linkage sialidase with a validated substrate panel | A broader pool of enzymatically accessible terminal sialic acid | Different hydrolysis rates among linkage and substrate classes |
| Ganglioside-associated sialic acid | Ganglioside-active sialidase followed by product-specific analysis | Sialic acid released from compatible glycolipid or ganglioside substrates | Ganglioside composition, membrane context, detergent, and substrate accessibility |
| Linkage or structural comparison | Parallel treatment with sialidases of different selectivities | Difference in signal or structure before and after defined enzyme treatments | Activity-unit comparability and equal access to the tested substrate |
Sialidases, also known as neuraminidases, cleave terminal sialic acid residues from compatible glycoconjugates. They are not universally interchangeable: linkage recognition, underlying glycan structure, steric accessibility, and the physical form of the substrate can all affect cleavage.
A broad-spectrum enzyme is suitable when maximizing release is the primary goal, whereas a linkage-selective enzyme is more appropriate when the difference between linkage classes is analytically important.
Gangliosides present a different substrate environment from soluble glycoproteins or oligosaccharides. Detergents, lipid aggregation, membrane-like structures, and glycan accessibility may influence the apparent activity of ganglioside sialidases.
After free sialic acid has been obtained directly or released from a glycoconjugate, sialic acid aldolase can provide a common route to pyruvate. The resulting pyruvate can be measured through an LDH-coupled NADH reaction or another compatible detection system.
| Product | Assay Role | Points to Confirm |
|---|---|---|
| Native Microorganism N-Acetylneuraminic Acid Aldolase | Cleavage of Neu5Ac to N-acetyl-D-mannosamine and pyruvate for enzymatic quantification | Direction of use, activity definition, pyruvate background, contaminating NADH oxidase, pH, and stability |
| Sialic Acid Aldolase (CgNal) | Reversible Neu5Ac aldol reaction for sialic acid detection or synthesis-oriented applications | Reaction direction, source, substrate concentration, equilibrium, and compatibility with the reporter reaction |
| Sialic Acid Aldolase (EcNPL) | Alternative recombinant aldolase for Neu5Ac conversion and assay-development comparison | Activity-unit definition, source, substrate scope, formulation, and scale requirements |
| Native Microorganism D-Lactate Dehydrogenase | Coupled conversion of pyruvate with an associated change in NADH/NAD+ | Pyruvate response, NADH oxidase contamination, pH overlap with aldolase, and signal linearity |
Aldolase products may be characterized in either the cleavage or synthesis direction. For a quantitative Neu5Ac assay, activity should be verified in the intended cleavage direction and under the complete coupled-reaction conditions.
A sialidase-based pretreatment does not automatically release every sialic acid form in a sample. Recovery depends on linkage, glycan structure, neighboring residues, substrate conformation, and enzyme access.
Release studies should consider:
The aldolase and LDH steps should be sufficiently rapid that the measured response reflects the available Neu5Ac rather than a slow auxiliary reaction.
Relevant checks include:
Practical interpretation: the assay result represents the sialic acid made accessible by the selected preparation and enzyme system. It should not be generalized to all sialic acid species unless recovery has been demonstrated across the relevant substrates.
| Product Group | Available Products | Best-Fit Use |
|---|---|---|
| Broad-linkage sialidases | BiNanH2; SpNanA | Release of multiple linkage classes for total-releasable sialic acid or broad glycan analysis |
| Linkage-selective sialidase | Ps26PSia | α2,6-focused release and comparative linkage analysis |
| Ganglioside sialidases | AuSialidase M2; AuSialidase S | Ganglioside and glycosphingolipid sample treatment |
| Sialic acid aldolases | Native NANA Aldolase; CgNal; EcNPL | Neu5Ac conversion, quantitative assay development, and synthesis-related workflows |
| Coupling enzyme | D-Lactate Dehydrogenase | Pyruvate-linked NADH detection in compatible coupled reactions |
Need Help Defining Your Sialic Acid Assay?
Share the intended measurand, sample type, expected linkage classes, glycoprotein or glycolipid context, detection format, and required production scale with our technical team.
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Q1. What is the difference between free and total sialic acid?
Q2. Is a sialidase required for every sialic acid assay?
Q3. Can one sialidase release all bound sialic acid?
Q4. How do I choose between broad-spectrum and linkage-selective sialidases?
Q5. What is the role of sialic acid aldolase?
Q6. Why is lactate dehydrogenase used in the assay?
Q7. Can aldolase activity measured in the synthesis direction predict assay performance?
Q8. Are special enzymes required for ganglioside samples?
Q9. Can Creative Enzymes help optimize a complete sialic acid assay?
