Tissue level studies indicate that bile is an important route of excretion. Significant levels have been demonstrated in the majority of body tissues. Although lincomycin appears to diffuse in the cerebrospinal fluid (CSF), levels of lincomycin in the CSF appear inadequate for the treatment of meningitis. Biosynthesis
Lincomycin is an antibiotic classified as a member of the lincosamide class, which typically features a L-proline amino acid derivative linked through amide group with an eight-carbon aminothio sugar. The two units 4-propyl-L-proline and the amino-octose, are each synthesized separately, and are then condensed by LmbD protein, and then further postcondensation reactions involving cleaving of mycothiol, deacetylation, and S-methylation finally yield lincomycin. The biosynthesis of the amino acid moiety of lincomycin, starts with tyrosine which is transformed to 4-propyl-L-proline by the consecutive action of LmbB1, LmbB2, LmbW, LmbA and LmbX proteins. 4-Propyl-L-proline is activated by LmbC and loaded into LmbN, a bifunctional peptidyl carrier protein, and is ready for condensation by LmbD. The biosynthetic pathway for production of the amino-octose moiety is almost fully elucidated although the order of the steps still needs further research. Condensation through a transaldolase (LmbR) of ribose 5-phosphate (C5) with fructose 6-phosphate or sedoheptulose-7-phosphate (providing a C3 unit) forms the octose (C8). Further transformations involving isomerization (LmbN), 1-phosphorylation (LmbP), 8-dephosphorylation (LmbK), guanosine diphosphate attachment at position 1 (LmbO), 4-epimerization (LmbM), 6-oxidation (LmbL), amination (LmbS), imine reduction (LmbZ) and 8-reduction, are performed to construct the amino-octose unit. LmbT protein exchange GDP by ergothioneine and the condensation with 4-propyl-L-proline and catalysed by LmbD can occur.
Periodic paralysis is a group of rare genetic diseases that lead to weakness or paralysis from common triggers such as cold, heat, high carbohydrate meals, not eating, stress or excitement and physical activity of any kind. The underlying mechanism of these diseases are malfunctions in the ion channels in skeletal muscle cell membranes that allow electrically charged ions to leak in or out of the muscle cell, causing the cell to depolarize and become unable to move.The symptoms of periodic paralysis can also be caused by hyperthyroidism, and are then labeled thyrotoxic periodic paralysis; however, if this is the underlying condition there are likely to be other characteristic manifestations, enabling a correct diagnosis. Types
Periodic paralysis is an autosomal dominant myopathy with considerable variation in penetrance, leading to a spectrum of familial phenotypes (only one parent needs to carry the gene mutation to affect the children, but not all family members who share the gene are affected to the same degree). Specific diseases include:
Hypokalemic periodic paralysis (Online Mendelian Inheritance in Man (OMIM): 170400), where potassium leaks into the muscle cells from the bloodstream. Hyperkalemic periodic paralysis (Online Mendelian Inheritance in Man (OMIM): 170500), where potassium leaks out of the cells into the bloodstream. Paramyotonia congenita (Online Mendelian Inheritance in Man (OMIM): 168300), a form which often accompanies hyperkalemic periodic paralysis, but may present alone. The primary symptom of paramyotonia congenita is muscle contracture which develops during exercise or activity. Paramyotonia congenita attacks may also be triggered by a low level of potassium in the bloodstream.