Thermostable (SULT1A1) and thermolabile (SULT1A3) phenol sulfotransferasesin human osteosarcoma and osteoblast cells

Sulfate conjugation is an important pathway in the metabolism of many drugs , xenobiotic compounds, and hormones, Sulfotransferases (SULTs) catalyze th ese reactions and have been detected and characterized in various human tis sues including the liver and small intestine. Substrates for SULTs that inc lude estrogen and thyroid hormones have well-established roles affecting sk eletal integrity and disease processes. We performed the following studies to determine the presence of SULTs in human osteoblast-like cells, and to c ompare their characteristics to SULTs expressed in other human tissues. Fou r osteosarcoma cell lines (SaOS-2, U2-OS, PR, and HOS-TE85) were screened f or the presence of four different SULT activities. Predominant activities w ere found for SULT1A1 in SaOS-2 cells, and SULT-1A3 in HOS-TE85 cells, Seve ral biochemical properties of each enzyme that included apparent K-m values , thermal stabilities, and responses to the inhibitors 2,6-dichloro-4-nitro phenol and NaCl were used to further characterize the SULT activities, High -performance liquid chromatography (HPLC) of the reaction products confirme d the known products of SULT1A1 and SULT1A3. When the mature human osteobla st HOB-03-CE6 cell line was tested for activity alone, the predominant acti vity was SULT1A3, with minimal SULT1A1. The results indicate that SULT1A1 a nd SULT1A3 are present in human osteosarcoma and mature osteoblast cell lin es, and that the characteristics of the osteosarcoma cell SULTs are similar to those expressed in other human tissues, SULTs may have regulatory roles in the deactivation of thyroid hormones or estrogenic compounds in bone, a nd thus may affect hormone action and bone responses in the human skeleton, (C) 2001 by Elsevier Science Inc. All rights reserved.