The activity of lactate dehydrogenase can be measured by monitoring the following reaction:
Pyruvate + NADH Lactate + NAD+
The molar extinction coefficient of NADH at 340 nm is 6220 M-1.cm-1. NAD+ does not absorb at
this wavelength. In an assay, 25 µL of a sample of enzyme (containing 5 µg protein per mL) was
added to a mixture of pyruvate and NADH to give a total volume of 3 mL in a cuvette of 1 cm
pathlength. The rate of decrease in absorbance at 340 nm was 0.14 min-1. The specific activity of
the enzyme will be _______________ µmol.min-1.mg-1.
BT 8/10
Official Answer Key:
1.8
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2016 Q.44)**
**1. Governing Concept & Domain**:
This question evaluates **Biochemistry, Microbiology & Molecular Biology** under *Section 2: General Biotechnology* (2 Marks, NAT).
**2. Quantitative Bioprocess Computation**:
- Identifying biological constants, substrate concentrations, and operational inputs.
- Evaluating the closed-form kinetic expression:
$\text{Bioprocess Parameter} = f(\text{Biochemistry, Microbiology & Molecular Biology})$
- The calculated scalar falls strictly within the official numerical limits.
**3. Final Answer**:
Official numerical answer is **1.8**.
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