Galatasaray kicked off the Emirates Cup with a 1-0 win over Porto on Saturday afternoon.
In a tale of three penalties, Felipe Melo scored the game's only goal with 20 minutes to play, converting from the spot after former Gunner Emmanuel Eboue had been fouled in the area.
Jackson Martinez had earlier seen a first-half spot-kick saved by Galatasaray goalkeeper Fernando Muslera.
Porto were given another big chance to draw level after 77 minutes but, after Danilo had been felled, Lucho Gonzalez dragged his penalty wide.
Galatasaray take on hosts Arsenal on Sunday while Porto entertain Napoli.
Emirates Cup table
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