Cytochrome components of plant microsomes

Area of Science:

• Plant biochemistry
• Spectrophotometry
• Electron transport chain

Background:

• Microsomal fractions are crucial for cellular metabolism and contain diverse electron transport components.
• Understanding plant cytochrome composition is vital for elucidating metabolic pathways and responses to environmental factors.

Purpose of the Study:

• To characterize the electron transport components within the microsomal fractions of cauliflower buds and mung bean hypocotyls.
• To compare the cytochrome profiles between these two plant species and investigate potential analogies with mammalian systems.

Main Methods:

• Utilized split-beam and dual wavelength spectrophotometry for analyzing microsomal fractions.
• Employed various reducing conditions, including ascorbate and dithionite, to identify and quantify cytochromes.
• Conducted binding studies (e.g., ethyl isocyanide, aniline) and redox potential measurements.

Main Results:

• Cauliflower microsomes contain ascorbate-reducible cytochrome b-559.5, cytochrome b5, and cytochromes P-450/P-420. The P-450 system shows similarities to mammalian microsomes.
• Mung bean microsomes possess an ascorbate-reducible cytochrome b-562, cytochrome b5, and a dithionite-reducible component, but lack detectable cytochrome P-450/P-420.
• A general analytical method for plant cytochromes was developed, revealing significant variations in type and quantity across different plant sources.

Conclusions:

• Cauliflower and mung bean microsomes exhibit distinct cytochrome compositions, particularly regarding the presence of cytochrome P-450.
• The cytochrome P-450 system in cauliflower microsomes appears analogous to that found in mammalian systems.
• Significant inter-plant variability exists in microsomal electron transport components, highlighting the need for species-specific analyses.