Golgi glycosylation enzymes

Abstract

From time to time the question is posed by colleagues and research pupils about an object blackened by the classical Golgi techniques [black reaction or reazione nera developed by C. Golgi to identify the Golgi Apparatus], “Is this a Golgi body?” I suggest the proper answer would be: “I do not think that your question has a meaning. It is framed in terms of an improbable hypothesis” (Baker 1953). This telling citation coincides with the end of the long-lasting Golgi controversy about its mere existence; it was finally resolved by the clear definition of the GA¹ as an ultrastructural entity (Dalton and Felix 1954). In fact, at these times the believers already recognized that the GA is likely to contain mono- and polysaccharides by virtue of specific histochemical staining (discussed by Bensley (1951)). The breakthrough to recognize the GA as the main cellular site of glycosylation can be traced back to the metabolic incorporation of glucose into cellularcomponents shown by autoradiography to occur in the GA (Neutra and Leblond 1966). The procedure applied by these authors was inspired by Palade’s pioneering work on the secretory pathway (Caro and Palade 1964). The next milestone in associating glycosylation mechanisms with the GA was the advent of fractionation techniques combined with identification of subcellular fractions by marker enzymes such as galactosyltransferase [EC 2.4.1.22]. In the late 1960s a number of groups introduced a corresponding enzyme to identify Golgi fractions which were morphologically assigned to the GA (for review see (1981)). The circle was then closed by the first immunocytochemical staining of the GA using antibodies to this enzyme (Berger et al. 1981), as shown in Fig. 1.