Immunoelectron microscopic localization of serine: pyruvate aminotransferase in rat eosinophile leukocytes.

Localization of serine: pyruvate aminotransferase [EC 2.6.1.51]; SPT in rat eosinophile leukocytes was investigated by protein A-gold technique. Thin sections of rat intestine were incubated with anti-SPT, followed by protein A-gold complex. Labelling with gold particles was seen on the specific granules of eosinophile leukocytes, in which 78% of the gold particles were localized on their paracrystalline cores and 22% on matrix, indicating that the main intragranular sites of SPT are the core. Other cell organelles such as nucleus and mitochondria were not labelled specifically. Quantitative analysis of labelling density in the subcellular compartments also confirmed that SPT is present exclusively in the specific granules.