Mr Wallace was the literature and publishing manager at national arts body, Creative Scotland, and had also been head of literature for the Scottish Arts Council for eight years.
Mr Rankin posted on Twitter: "Saddened and shocked by news of Gavin Wallace's death.
"I met Gavin many times. Passionate about writing and writers, a great guy to drink with, and a great loss to all of us in Scotland."
Mr Wallace's sister, the writer Morag Joss, said the family were "devastated and shocked" by his death.
Author Julie Bertagna said: "I'm gutted to hear Gavin Wallace has died. Lovely, lovely man. Friend and trusted adviser to so many authors."
Iain Munro, director of creative development at Creative Scotland, said: "Gavin has long been a central figure in Scotland's literature world, greatly known and respected by everyone who has had the good fortune to work with him. Our heartfelt condolences go to Gavin's partner Pauline and their two sons."