Sialidase, also known as Neuraminidase (NA) in virology, is an enzyme that hydrolyzes the glycosidic bonds of sialic acid (N-acetylneuraminic acid). This enzyme is widely present in viruses, bacteria, and mammalian cells, playing a key role in various physiological and pathological processes.

1. A Key Biomarker for Bacterial Vaginosis (BV) Diagnosis

In gynecological IVD reagent development, utilizing enzymatic differences among microbiota for differentiation is a core biochemical diagnostic strategy.

• Negative Control: The dominant bacterial flora (e.g., Lactobacilli) in the vagina of healthy women typically do not produce sialidase.

• Positive Indicator: BV-associated pathogenic bacteria (e.g., Gardnerella, Prevotella) secrete high-activity sialidase.

Therefore, precisely capturing sialidase activity with chromogenic substrates can provide objective, quantifiable biochemical evidence for BV diagnostic kits.

2. Role in Viral Infection

Taking the influenza virus as an example, it has two major glycoproteins on its surface:

• Hemagglutinin (HA): Mediates virus binding to host cells.

• Neuraminidase (NA): Cleaves sialic acid residues, promoting the release of newly formed virus particles.

NA is the core target for anti-influenza drugs (such as oseltamivir and zanamivir). Detecting NA activity is crucial for virology research and antiviral drug development.

X-NeuNAc is a specific chromogenic substrate for sialidase (neuraminidase). Its working principle is clear and efficient:

1. Specific Enzymatic Cleavage: Sialidase specifically recognizes and hydrolyzes the sialic acid glycosidic bond in the substrate.

2. Chromogen Release: The cleavage releases the 5-bromo-4-chloro-3-indole product.

3. Signal Generation: This product, in the presence of an oxidant (such as diazonium salt traditionally required in formulations), rapidly forms a stable blue-purple precipitate, enabling visualization of activity.

When active sialidase is present in the sample, a distinct blue-purple color reaction can be observed, indicating the presence of BV-associated bacteria or other sialidase-positive pathogens.

When the formulation contains diazonium salt, the released 5-bromo-4-chloro-3-indoxyl reacts instantly with the diazonium salt to form different colored substances. For example, adding Fast Violet B Salt to the formulation will generate a purplish-red substance.

Of course, other diazonium salts can be added to the formulation to generate different colors, providing a wider choice of color.

Our company also offers a substrate that directly yields a purplish-red color after enzymatic cleavage without requiring diazonium salt in the formulation: the BV Substrate (GST1008). This avoids the use of diazonium salts, making the formulation simpler, the product more stable, and the shelf life longer.