Extracting proteins from plants is not the same as extracting proteins from animal sources. There is a very different set of factors that you will need to consider in order to properly process plant proteins. This post explores some of the key ways in which plant-based protein extraction differs from animal-based protein extraction, and details some of the ways you can overcome these differences.
Breaking Down the Cell Walls
The biggest difference between extracting proteins from plant cells vs. animal cells is that with plant cells, you have to contend with a cell wall. These walls contain interfering agents, such as proteases, which make it difficult to get accurate results from the cell unless certain steps are taken. Before you can begin the extraction process, you will need to disrupt the cell wall of plant cells.
On top of that, the way you go about protein extraction can vary depending on the type of plant cell, such as a fruit, seed, or leaf. The type of the plant, as well as its age, can also factor into which method should be used to break down the cell wall. For example, older plant cells will often contain more secondary metabolites, which can throw off your results.
While there are a number of ways in which you can disrupt cell walls, there are two primary methods which you should concern yourself with: chemical lysis and mechanical lysis.
Mechanical homogenization can be effectively used to break apart plant cell walls to retrieve the proteins and separate out the starches. In both open-blade mills and rotor-stator homogenizers, blades are used to shear the cells apart, disrupting the rigid cell wall and releasing the proteins. This is also referred to colloidal milling. During the wet milling process, enzymes and other chemicals can be used to separate and stabilize the proteins from the starches. Even though the blades are completely thorough at disrupting the cell wall and shredding the contents, the proteins are left virtually unscathed.
Chemical lysis is generally considered to be the easiest (if somewhat pricier) approach to breaking down cell walls. Chemical buffers are also a more stable and repeatable way of extracting proteins.
One advantage to chemical lysis is that there are wide variety of buffers available, so depending on the type of plant cell you are using, there is going to be one to meet your needs. For example, lytic enzymes are commonly used for chemical lysis and come in a number of variations that are ideal for plants. Cellulase and Trypzean are good examples of lytic enzymes that work well with plant cells.
To better understand which buffer is right for your experiment, refer to our sample preparation guide.
Please note that there may be times in which both chemical and mechanical lysis may be necessary. When dealing with particularly resilient cells, for example, it may make more sense to use a combination of the two techniques.
Extracting proteins from different sources, be it animal or plant, requires specific methods and certain conditions. The structure of the cells and the environment in which they are found can have a dramatic effect on the results of any that is performed, including Western Transfer and blot tests. Ensuring the accuracy of the test is essential. Utilizing the right method to break down the plant cell walls, while still protecting the proteins from damage before and during the test is the ultimate goal. Before beginning any test make sure the source of the protein and the requirements of extraction for that source are followed to the letter.