Distribution of phosphatases in the golgi region and associated structures of the thoracic ganglionic neurons in the grasshopper, Melanoplus differentialis

Evidence of acid phosphatase in the cytoplasm as a distinct entity

A study of subcellular acid phosphatase distribution in mammalian tissues shows that isozymes with specific functions are compartmentalized in the cells. The enzyme may be generalized into two types: type A and type B. They are shown by several means to be distinct entities. Type A is confined to the cytoplasm and is inhibited by Cu2+, HCHO, and the coupling agents (for enzyme staining) fast blue RR salt and fast Garnet GBC salt (newly discovered inhibitors), but is insensitive to fluoride and L-(+)-tartrate. Type B is localized in the organelles, presumably lysosomes, in both soluble form and membrane-bound form, with inhibitor sensitivity exactly opposite to that of type A enzyme. Types A and B consist of different sets of isozymes, with sensitivities to inhibitors resembling those observed with the crude extracts of subcellular fractions. Acid phosphatase that exhibits a phosphoryl transfer property was identified as type A enzyme. Type A enzyme has a slightly higher optimal pH and is inhibited by alloxan, whereas for type B, the addition of alloxan broadens the optimal pH to a higher range and elevates the activity of pH 7.4 from negligible to about 30-40% of that obtained under optimal conditions. The alloxan-mediated elevation of type B enzyme activity to this level at the physiological pH may be of considerable significance. Type B enzyme has a high affinity for metabolic intermediates and nucleotides, while type A has an extremely low affinity for these substrates. Cytoplasmic acid phosphatase (type A) is a significant enzyme population and its activity is not related to the lysosome density in the cells. Type A enzyme in the cytoplasm is thus shown to be an entity distinctly different from type B enzyme in the lysosomes. These findings suggest that the physiological functions of type A acid phosphatase, such as metabolic regulatory processes, merit further studies because of the phosphoryl transfer activity and cytoplasmic localization of the enzyme.

Cytochemical localiztion of nucleoside diphosphatase and thiamine pyrophosphatase activities in the rabbit corneal endothelium

Localization of NDPase and TPPase activities in the rabbit corneal endothelium was investigated by cytochemical methods. After incubation at both pH 7.0 and 8.0, the NDPase activity was detected in cisternae of ER, nuclear envelope, and Golgi saccules, while the TPPase activity was demonstrated only in Golgi saccules. The reaction products of both enzymes were decreased when incubated at pH 8.0. The NDPase activity was inhibited by uranyl nitrate but not by sodium fluoride, while the TPPase was inhibited by fluoride but not by uranium.

Growth and differentiation of cytoplasmic membranes in the course of lipoprotein granule synthesis in the hepatic cell. I. Elaboration of elements of the Golgi complex

The synthesis of "very low" density lipoprotein in liver cells is characterized by the fact that the synthesized products, mostly triglycerides, are processed in the form of discrete, size-limited granules or globules, about 400 A in diameter. The present investigation has been made possible in part by the use of a fixative (OsO(4) in bidistilled H(2)O at pH 6.0, in the absence of electrolytes) particularly effective in preserving cytoplasmic membranes and lipids, and giving them high stainability and differential contrast. Under these technical conditions, the lipoprotein granules retain their morphology and high density to electrons practically unaltered, and may serve as tracers in determining their route of transport from the sites of synthesis, starting at the rough-smooth ER junctions, to the lumen of Golgi concentrating vesicles. From the observations, it may be deduced that, along with lipoprotein granule synthesis and transport, there are also production and transfer of new membranes in the form of tubular extensions of smooth ER network which, by progressive fusion and coalescence, participate in the elaboration of fenestrated plates and solid Golgi sacs. In contradistinction to the entire process of liver lipoprotein granule synthesis, transport, and segregation, as reported in the present paper, appears to constitute a developmental sequence which includes the following communicating compartments, in consecutive order: cisternae of rough ER where proteins and possibly phospholipids are synthesized, smooth ER network where triglycerides are synthesized and transported in the form of dense granules, fusion of smooth ER tubular extensions into Golgi fenestrated plates, and further coalescence into solid Golgi sacs, ending in the segregation of the granules in appended concentrating vesicles, or detached "secretory vesicles." It seems that it is this progressive evolution in growth and configuration of membranes which is reflected in the so called polarity, from forming to mature faces, of the Golgi apparatus.