Adiponectin receptors, divided into Adipo1 and Adipo2, were initially classed as GPCR on the basis of hydropathy analysis suggesting seven transmembrane domains. However, they appear to be present in the cell membrane in a topology inverted compared to the 7TM GPCR. The study from Vasiliauskaite-Brooks  and colleagues suggests that Adipo1 and Adipo2 exhibit ceramidase activity. They report that adiponectin binding to Adipo2 enhances this ceramidase activity, providing in silico evidence for this mechanism. It is possible, therefore, that adiponectin receptors may belong to a unique class of catalytic receptor rather than GPCR.
 Vasiliauskaité-Brooks et al. (2017). Structural insights into adiponectin receptors suggest ceramidase activity. Nature, 544(7648):120-123. [PMID: 28329765]
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