Enzyme’ characterization is important for understanding metabolism as their catalytic role and regulation determines the flow of mass and homeostatic control in biological systems. It is particularly pronounced well in case with enzymes associated with basic metabolic pathways which made a Canadian researcher to apply this fact in castor metabolism to study an enzyme called pyruvate kinase and its materialistic regulation by proteolytic enzymes in sub-cellular compartments called leucoplasts.

Proteins are in general regulated from their activities by proteolytic degradation,chemical modification,cell sequestration etc and pyruvate kinase chosen as model system in this scientific study was evaluated for its degradation by protease called cysteine endopeptidase.A crude preparation of protein fraction from castor endosperm over different developmental stages of castor seed was made. Protein profiling data revealed an accelerated degradation of the enzyme in wild preparations but when samples were treated with probe inhibitors specific for endopeptidases,a converse result was noticed, by which the researcher was able to conclude that it is the cysteine endopeptidase, acts as a negative regulator of pyruvate kinase in castor seed development, with temporal regulation in its activity inspite of a consistent synchronous existence with pyruvate kinase at the extra-plastid region.He further reported that a regularity in pyruvate kinase driven functional castor physiology was attributed to enzyme’s presence.

This is an interesting study in this oilseed crop where an entire picture of molecular events pertaining to vital enzymes has been presented and enables us to produce a resolved map in seed maturation and development.However attention is required to profile the associated molecular factors driving this complex phenomenon without generating an exaggerated  interwoven metabolic network to pose difficulties in selection and isolation of members in the cellular tie ups.

For reference: Plant Physiol. (1991) 97, 1334-1338