Q.35 Protein concentration of a crude enzyme preparation was 10 mg mL-1.
10 µL of this sample gave an activity of 5 µmol min-1
under standard assay conditions. The specific activity of this crude enzyme
preparation is ________ units mg-1.
Introduction to Specific Activity in Crude Enzyme Preparations
Specific activity of crude enzyme preparation reveals enzyme efficiency amid impurities. For a sample at 10 mg mL⁻¹ protein where 10 µL gives 5 µmol min⁻¹ activity, compute 50 units mg⁻¹ to assess purity in biochemistry assays. This key metric aids IIT JAM biotech aspirants mastering enzyme kinetics.
Why Calculate Specific Activity?
Specific activity = Activity (units) / Protein (mg), tracking purification progress.
- Crude enzyme preparations start low due to inhibitors and impurities.
- Units represent µmol product min⁻¹.
- Monitors removal of non-enzyme proteins.
- Essential concept for biotech exams like GATE and IIT JAM.
Step-by-Step Calculation
Convert volume: 10 µL = 0.01 mL
Protein in sample: 0.01 mL × 10 mg mL⁻¹ = 0.1 mg
Activity: 5 µmol min⁻¹ = 5 units
Specific Activity: 5 units / 0.1 mg = 50 units mg⁻¹
This quantifies enzyme purity; crude extracts show lower values due to contaminants.
Detailed Solution Walkthrough
Protein amount: 10 µL = 0.01 mL, so 0.01 × 10 = 0.1 mg
Activity: 5 units (given).
Specific activity: 5 / 0.1 = 50 units mg⁻¹.
No options provided; direct numerical answer fits fill-in-the-blank format.
Applications in Enzyme Purification
Rise in specific activity signals purification success—crude may show 0.2 U mg⁻¹ but reach 50+ after chromatography.
| Stage | Protein (mg mL⁻¹) | Activity (U mL⁻¹) | Specific Activity (U mg⁻¹) |
|---|---|---|---|
| Crude | 10 | 500 | 50 |
| Purified Example | 1 | 100 | 100 |
Exam Tips for IIT JAM Biotech
- Practice crude enzyme preparation problems.
- Watch unit conversions carefully.
- Important keywords: specific activity calculation, enzyme units mg⁻¹.
