protein degradation - (Dec/28/2006 )

Hi..I had a small question:
woyldn't it be thermodynamically more favourable for a cell to phagocytose and degrade the proteins through enzymes or in excotytosis of proteins rather than complicated degradation pathways like Ubiquitination and sumoylation?

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do you think the process of phagocytosis, and enzyme production, etc are really that much simpler in terms of thermodynamics? do you think it's thermodynamically 'cheap' for the cell to use exocytosis? that must take a pretty enormous amount of energy, just for the bare physical components, not to mention all the signaling effector molecules involved behind the scenes

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it is also in terms of thermodynamics if you have an high order of regulation; so gating proteins to proteasomes by ubiquitinilation or SUMOylation is a question of specificity of regulation in a multistep process integrated in a functional network; I suppose that simple enzymatic degradation without regulated sorting has not many switches of regulation; phagocytosis is rather to acquire and degrade proteins from outside than for homekeeping proteins

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