NUCLEOSIDE PHOSPHATASE AND THIAMINE PYROPHOSPHATASE ACTIVITY OF RABBIT GOLGI APPARATUS

The Golgi associated nucleoside phosphatase which is demonstrable in rabbit pancreatic islet cells at alkaline pH using briefly postfixed cryostat sections and a modified Padykula-Herman incubation solution rapidly hydrolyzes uridine triphosphate (UTP) as well as uridine (UDP) and inosine diphosphate (IDP), but not thiamine pyrophosphate (TPP). Staining in the Golgi apparatus of islet cells was markedly attenuated when a lead incubation solution was employed at pH 7.2 with these same nucleoside-phosphates as substrates. The enzyme was not demonstrable in sections cut from tissue blocks fixed for 24 hours in formalin. This enzyme was distributed in the Golgi apparatus of some cellular elements of many other rabbit tissues. In rabbit cortical neurons a different Golgi enzyme was demonstrated which at alkaline pH hydrolyzed TPP but not UTP, IDP or UDP. This enzyme was also demonstrable with the lead method at pH 7.2 and under these conditions hydrolyzed IDP and UDP as well as TPP, but not UTP. The neuronal enzymatic activity was much less formalin-sensitive than that in pancreatic islet Golgi apparatus surviving in 24-hr formalin-fixed tissue blocks. This latter enzyme could be demonstrated in addition to brain only in the Golgi apparatus of hypophysis and epididymis. Differences in substrate specificity and of response to adjuvants as well as the differences in distribution confirm that these are two distinct enzymes.