IDS Human

What is human iduronate-2-sulfatase (IDS) and what is its biological role?

Iduronate-2-sulfatase (IDS) is a lysosomal enzyme encoded by the IDS gene located on chromosome Xq28. It plays a critical role in the degradation pathway of glycosaminoglycans (GAGs), specifically catalyzing the removal of sulfate groups from these complex carbohydrates .

The enzyme's core function involves cleaving sulfate groups from specific substrates, which is essential for proper cellular metabolism. Without this activity, undegraded or partially degraded GAGs accumulate within lysosomes, leading to cellular dysfunction. This enzyme is particularly important in connective tissue metabolism, where proper GAG turnover is essential for tissue homeostasis.

Methodologically, IDS activity can be assessed using artificial substrates such as 4-nitrocatechol sulfate, which allows researchers to quantify the enzyme's ability to remove sulfate groups through spectrophotometric or fluorometric assays .

How is IDS deficiency related to Hunter syndrome?

Mucopolysaccharidosis II (MPS II), commonly known as Hunter syndrome (OMIM 309900), is a rare X-linked recessive lysosomal storage disease caused by mutations in the gene encoding iduronate-2-sulfatase . This genetic defect results in impaired degradation of GAGs, leading to their progressive accumulation in tissues and organs.

The pathophysiology involves:

• Disruption of cellular metabolism due to GAG accumulation

• Progressive tissue and organ damage

• Varying clinical presentations based on mutation severity

Research approaches for studying this relationship include:

• Genetic analysis to identify specific mutations in the IDS gene

• Enzyme activity assays to quantify residual IDS function

• Biomarker measurement to track disease progression

• Animal models to study pathophysiological mechanisms

Hunter syndrome represents a classic example of how a single enzyme deficiency can impact multiple organ systems, making it an important model for understanding lysosomal storage disorders more broadly.

What analytical methods are used for detecting and measuring IDS in human samples?

Researchers have developed various validated analytical methods for measuring IDS in human samples. For quantification of free and total desmosine and isodesmosine in human urine (which can relate to IDS activity), two principal approaches are commonly employed :

• Analysis against calibrators containing authentic analyte in surrogate matrix

• Analysis containing surrogate analyte in authentic matrix

Modern methodologies primarily utilize liquid chromatography-tandem mass spectrometry (LC-MS/MS) for high sensitivity and specificity. This technique allows researchers to detect even small quantities of the enzyme or its metabolites in complex biological samples .

For enzyme activity measurements, researchers commonly use:

• Fluorometric assays with specific substrates

• Immunological techniques for protein quantification

• Genetic analysis methods for mutation identification

These analytical approaches provide researchers with tools to accurately assess IDS levels and activity in clinical and experimental settings.

What approaches exist for producing active human IDS for research purposes?

Several expression systems have been developed to produce active human IDS, each with distinct advantages and challenges. Plant-based expression systems have shown particular promise in recent studies :

Researchers have demonstrated that Nicotiana benthamiana can be used to express high levels of biologically active recombinant human IDS (hIDS). The production of active IDS is challenging because it requires cotranslational modification by a formylglycine-producing enzyme encoded by sulfatase modifying factor 1 (hSUMF1) at the Cys84 residue, which converts it to C(alpha)-formylglycine .

Methodologically, researchers have successfully:

• Designed specialized expression constructs (e.g., BiP-GB1-L-dCBD1-2L-8xHis-L-6xHis-3L-EK-hIDS-HDEL)

• Co-expressed turnip crinkle virus gene silencing suppressor P38

• Utilized GB1-fused human calreticulin as a folding enhancer

• Co-expressed hSUMF1 for necessary cotranslational modification

• Purified using Ni²⁺-NTA affinity resin followed by enterokinase treatment

• Removed N-terminal fragments using microcrystalline cellulose beads

The purified active form of hIDS can successfully cleave sulfate groups from artificial substrates at levels comparable to commercial IDS expressed in animal cells .

What are the challenges in validating IDS-related biomarkers for clinical applications?

Validating IDS-related biomarkers for clinical applications presents several methodological challenges that researchers must address :

• Analytical validation requirements: Methods must demonstrate accuracy, precision, specificity, and reproducibility across different laboratories and sample types. This involves rigorous validation of quantification methods for both free and total (free+peptide-bound) forms of biomarkers .

• Population variability: Researchers must account for natural variations in biomarker levels across different populations, requiring well-designed studies with appropriate controls (e.g., healthy never-smokers, healthy current-smokers, and COPD patients) .

• Longitudinal assessment: To establish prognostic value, studies must track biomarker changes over time in relation to disease progression and therapeutic interventions .

• Standardization challenges: Different analytical platforms and methodologies may yield different results, necessitating standardization efforts.

The validation process typically involves:

• Comparison of different quantification approaches

• Assessment of matrix effects in biological samples

• Determination of detection and quantification limits

• Validation across multiple laboratories

Table data extrapolated from methodological descriptions in validation studies

How can machine learning approaches enhance IDS-related research?

Machine learning (ML) approaches offer powerful tools for advancing IDS-related research, particularly in predicting novel pharmacological activities and biomarker applications :

Researchers have demonstrated that ML models can be developed using only identification numbers provided by databases like PubChem (CIDs and SIDs), allowing drug development researchers to easily identify new functionalities of compounds without requiring complex structural or chemical data inputs .

Methodological approaches include:

• Extracting compound identifiers and corresponding activity data from bioassays

• Filtering datasets by combining with solubility bioassay data to improve signal-to-noise ratio

• Applying scikit-learn algorithms to develop predictive models

• Validating models using multiple performance metrics

Performance metrics for these ML models have shown promising results:

• 83.82% Accuracy (standard deviation: 5.35)

• 87.9% Precision (standard deviation: 5.04)

• 77.1% Recall (standard deviation: 7.65)

• 82.1% F1 score (standard deviation: 6.44)

• 83.4% ROC (standard deviation: 5.09)

These approaches can be applied to IDS research to identify potential new inhibitors or activators, predict compound interactions with the enzyme, and develop novel therapeutic approaches for conditions like Hunter syndrome.

What are the critical post-translational modifications required for IDS activity and how can they be ensured in recombinant expression?

The activity of human iduronate-2-sulfatase critically depends on specific post-translational modifications, particularly the conversion of Cys84 to C(alpha)-formylglycine by the formylglycine-generating enzyme encoded by sulfatase modifying factor 1 (hSUMF1) . This modification is essential for catalytic activity.

Methodological approaches to ensure proper modifications include:

• Co-expression strategies: Simultaneously expressing IDS with hSUMF1 to ensure the critical formylglycine modification occurs .

• Expression system selection: Different expression systems vary in their capacity to perform complex post-translational modifications. Plant-based systems like N. benthamiana have shown promise .

• Construct optimization: Designing expression constructs that promote proper protein folding and accessibility of modification sites:

  • Inclusion of appropriate signal peptides

  • Strategic placement of purification tags

  • Incorporation of folding enhancers

• Folding enhancement: Co-expression with chaperones like GB1-fused human calreticulin (GB1-CRT1) .

• Verification methods: Confirming modifications through:

  • Mass spectrometry analysis

  • Activity assays with specific substrates

  • Comparison with native enzyme characteristics

The successful application of these approaches has been demonstrated in plant expression systems, yielding recombinant IDS with activity levels comparable to commercial preparations from animal cells .

How can researchers leverage Google's "People Also Ask" data to identify emerging research questions about human IDS?

Google's People Also Ask (PAA) feature represents a valuable but underutilized resource for researchers to identify emerging questions and knowledge gaps in specialized fields like IDS research :

PAA appears in approximately 51.85% of all searches (as of August 2024), providing researchers with insights into common questions and conceptual relationships within a research domain .

Methodological approaches for leveraging PAA data include:

• Systematic extraction of PAA questions: Using specialized tools like Semrush's Keyword Magic Tool to gather comprehensive PAA question datasets related to IDS research .

• Cluster analysis: Analyzing question patterns to identify conceptual frameworks and relationship networks between questions, providing insights into how research topics are interconnected .

• Question hierarchy mapping: Identifying basic versus advanced questions to structure research communications that address audience needs at different knowledge levels .

• Gap analysis: Comparing existing literature against frequently asked questions to identify underserved research areas.

• Research planning: Using PAA data to design studies that address common knowledge gaps and anticipate future questions in the field .

This approach allows researchers to align their work with actual information needs, potentially increasing research impact and addressing overlooked questions in the field of human IDS research.

What are the comparative advantages of different expression systems for producing active human IDS?

Various expression systems have been explored for producing active human IDS, each offering distinct advantages and limitations for research applications :

Table compiled based on research findings and methodological considerations

Plant-based systems have shown particular promise, as demonstrated in recent research using N. benthamiana. When co-expressed with hSUMF1, turnip crinkle virus gene silencing suppressor P38, and GB1-fused human calreticulin (GB1-CRT1), these systems can produce highly active IDS comparable to commercial preparations from animal cells .

The methodological advantages of plant expression systems include:

• Cost-effective scalability

• Ability to perform complex post-translational modifications

• Lower risk of contamination with human pathogens

• Potential for field-scale production

These comparative advantages make plant-based systems particularly attractive for producing IDS for both research and potential therapeutic applications.