1. 10 g of a plant material is extracted in 100mL of a suitable buffer. On performing an assay for amylase
activity, 100μl extract produced 6 μmoles glucose in 30 minutes of incubation. One unit of amylase activity
is defined as the amount of enzyme required to produce 1μmole of glucose per minute. The amylase activity
(units/g) of the material is:
1. 60
2. 200
3. 20
4. 600

How to Calculate Amylase Activity in Plant Extracts: Step-by-Step Guide

Enzyme activity assays are fundamental to understanding the biochemical properties of biological samples. When measuring amylase activity, it’s essential to interpret experimental data correctly and apply standard definitions to calculate enzyme units per gram of material.

Let’s address the following question:

Question:

10 g of a plant material is extracted in 100 mL of a suitable buffer. On performing an assay for amylase activity, 100 μL extract produced 6 μmoles glucose in 30 minutes of incubation. One unit of amylase activity is defined as the amount of enzyme required to produce 1 μmole of glucose per minute. What is the amylase activity (units/g) of the material?

Options:

1. 60

2. 200

3. 20

4. 600

Step-by-Step Solution:

1. Understand the definition of enzyme activity:

• 1 unit of amylase activity = 1 μmole of glucose produced per minute

2. Calculate the rate of glucose production:

• Given:

  • 100 μL of extract produces 6 μmoles of glucose in 30 minutes

• So the rate =

  6 μmoles30 minutes=0.2 μmoles/min\frac{6\ \mu\text{moles}}{30\ \text{minutes}} = 0.2\ \mu\text{moles/min}30 minutes6 μmoles​=0.2 μmoles/min

This means that 100 μL of the extract has 0.2 units of amylase activity.

3. Scale to total extract volume:

• Total extract volume = 100 mL = 100,000 μL

Now, if 100 μL has 0.2 units, then:

Total activity in 100,000 μL=(0.2100)×100,000=200 units\text{Total activity in 100,000 μL} = \left(\frac{0.2}{100}\right) \times 100,000 = 200\ \text{units}Total activity in 100,000 μL=(1000.2​)×100,000=200 units

4. Calculate activity per gram of plant material:

• The extract was made from 10 g of plant material

• Therefore, activity per gram:

200 units10 g=20 units/g\frac{200\ \text{units}}{10\ \text{g}} = 20\ \text{units/g}10 g200 units​=20 units/g

✅ Correct Answer: (3) 20

Why This Matters: Understanding Enzyme Assays

This type of calculation is common in biochemistry, plant physiology, and molecular biology. Measuring enzyme activity helps researchers:

• Evaluate metabolic rates

• Compare activity across conditions (e.g., stress, light, temperature)

• Quantify enzyme production in genetically modified organisms

Understanding how to calculate enzyme activity per gram ensures accurate reporting of biochemical data and allows for meaningful comparisons across experiments.

Summary

To calculate amylase activity (units/g):

1. Use the definition of enzyme units (μmole/min)

2. Determine the rate of product formation from assay data

3. Scale the result to the total volume of the extract

4. Divide by the weight of the original plant material

Answer: The amylase activity is 20 units per gram.