Activation barriers, compartmentalized

A membrane is a semipermeable barrier whose function is to compartmentalize metabolic processes, maintain pH differences on either side, control osmotic pressure and ionic gradients, provide a surface or environment for the stabilization of active biomolecules, provide tissue discrimination, and allow selective access as well as egress to specific metabolites. 

Biotinidase activity in cerebrospinal fluid and the brain is very low. This suggests that the brain may not recycle biotin effectively and depends on biotin transported across the blood-brain barrier. Several symptomatic children who have failed to exhibit peripheral lactic acidosis or organic aciduria have had elevated lactate or organic acids in their cerebrospinal fluid. This compartmentalization of the biochemical abnormalities may explain why the neurological symptoms usually appear before other symptoms. Peripheral metabolic ketoacidosis and organic aciduria subsequently occur with prolonged metabolic compromise. 

The distribution of a polymer in the body, the rate of its clearance, the site and time duration of its retention, i.e., all the basic factors determining the availability of a medical polymer for biological activity may be understood as resulting from its partitioning at compartmental barriers. These particular barriers may have various compositions (see below) but mostly thrir crossing includes some means of crossing of a biological membrane, which will be briefly characterized below. 

Biocatalyst limitations Transport barriers - diffusion trough the cell membrane Permeability issues Highly complex cellular system Often product formation growth-associated Measurement and stability of enzyme activity Compartmentalization in some cases... 

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