| Abstrakt: |
In an attempt to characterize the soluble alkaline phosphatase in rabbit lung, we have compared its activity to that of intestine, liver, bone, kidney, spleen and serum. The pulmonary alkaline phosphatase consists of isoenzymes with isoelectric points (pI) at pH 5. 0, 5. 5 and 5. 8 which are distinct from the soluble isoenzymes of the other tissues and, by this criterion, appear to be organ specific. The isoenzyme with a pI of 5. 8 has an apparent molecular weight of 185, 000 daltons and is found almost exclusively extracellularly in the airways. The isoenzyme with a pI of 5. 5 (mol. wt. = 185, 000 daltons) is distributed more equally between pulmonary tissue and the airways, and the isoenzyme of pI equal to 5. 0 (mol. wt. = 210, 000 daltons) is located entirely within the lung tissue. The isoenzymes present in the airways are closely related in spite of their different isoelectric points. In addition to their apparent molecular weights, they have similar apparent K values and thermostabilities. The difference in isoelectric points is probably due to different sialic acid contents since digestion of the two alkaline phosphatases in the airways with neuraminidase gives rise to a single form with a pI of 7. 6. [ABSTRACT FROM AUTHOR] |
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