cell biochemistry and function Cell Biochem Funct 2003; 21: 81–84. Published online 1 November 2002 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/cbf.997 Human cutaneous melanoma expresses a significant phosphate-dependent glutaminase activity: A comparison with the surrounding skin of the same patient Darwin Pinheiro Machado Zacharias 1 , Manuela Maria Ramos Lima* ,2 , Alcione Lescano Souza Jr. 2 , Ivan Dunshee de Abranches Oliveira Santos 1 , Milvia Enokiara 1 , Nilceo Michalany 1 and Rui Curi 2 1 Federal University of Sa ˜o Paulo (UNIFESP), Brazil 2 Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sa ˜o Paulo, Sa ˜o Paulo, SP, Brazil The protein content and the activity and type of phosphate-dependent glutaminase were determined in freshly pigmented lesions obtained from human melanoma and adjacent skin. Significant phosphate-dependent glutaminase activity was found in both the melanoma and non-pigmented adjacent skin areas. A comparison between the pigmented and adjacent skin areas suggests the occurrence of gradual metabolic changes that result in an increased protein content in the centre of the neoplasia. The presence of a kidney-type glutaminase (K m of 2–5 mM) indicates a high sensitivity of the melanoma to variations in glutamine plasma levels (0.6 to 1 mM). These data lead us to postulate that glutamine supply is an important factor for melanoma cell proliferation, being a source of nitrogen for DNA and RNA synthesis. The intense neovasculariza- tion observed in melanoma ensures the oxygen supply that is required for glutamine oxidation. These findings support the proposition that glutamine is an important fuel for melanoma. Copyright # 2002 John Wiley & Sons, Ltd. key words — cutaneous melanoma; glutamine; phosphate-dependent glutaminase activity INTRODUCTION Investigation of physiopathological aspects of mela- noma is mostly restricted to formalin fixation of the removed primary lesions. There is a need to find other methodologies to examine immunological and meta- bolic aspects of the tumour tissue. The melanoma itself and the skin surrounding it allow us to study concomitantly the two easily separated areas. There- fore, it is possible to have samples of the diseased tis- sue and the respective control from the same patient. Cutaneous melanoma presents a characteristic pig- mentation that allows us to differentiate their macro- scopic limits. Factors of poor prognosis such as the infiltration of neoplastic cells (vertical phase) in the deepest layers of the skin, 1 ulceration, 2 suppression of T lymphocytes 3–5 and neovascularization 6 can then be examined. The intense neovascularization sup- plies oxygen at a sufficient rate to ensure the high aggressiveness of the melanoma in the phase of vertical growth, in that the cells proliferate very quickly. The cutaneous melanoma, due to its fast growth in the phase of vertical infiltration, consumes high amounts of ATP. The main energy substrates for the tumour cells and for normal rapid proliferating cells such as lymphocytes and enterocytes are glucose and glutamine. 7–14 Glutamine participates in protein synthesis and through glutaminolysis generates ATP and precursors for DNA and RNA synthesis. 15 The key enzyme of glutaminolysis is phosphate-dependent glutaminase. 16 Despite the information noted above, there are no studies on glutaminase activity in human melanoma. In the present study, glutaminase activity was measured in both the pigmented lesion and the adjacent skin area of freshly obtained human cuta- neous melanoma. Received 5 March 2002 Copyright # 2002 John Wiley & Sons, Ltd. Accepted 23 May 2002 * Correspondence to: Manuela M. Ramos Lima, Laborato ´rio de Fisiologia Celular, Departamento de Fisiologia e Biofı ´sica, ICB, USP, 05508-900, Sa ˜o Paulo, SP, Brasil. Tel: 55-11-30917245. Fax: 55-11-30917285. E-mail: ruicuri@fisio.icb.usp.br