The phrase "act as a speaker" is correct and usable in written English.
You can use it when referring to someone taking on the role of a speaker in a discussion, presentation, or event.
Example: "During the conference, she was asked to act as a speaker on the topic of climate change."
Alternatives: "serve as a speaker" or "function as a speaker".
He has acted as a speaker for GlaxoSmithKline.
JC has acted as a speaker for Eisai, Forest, Janssen, Novartis, Pfizer and Lundbeck.
Chiara Paglino has acted as a speaker for Pfizer Oncology, Hoffmann-La Roche, GSK and Bayer-Schering Pharma.
ML has acted as a speaker for Servier and Astra-Zeneca.
VG has acted as a speaker or consultant for Pfizer Oncology, Novartis, GSK, Hoffmann-La Roche, Astellas, Aveo Pharmaceuticals, and Bayer-Schering Pharma.
AS has acted as a speaker for, consulted to, or received grant support from: Astellas, Bayer, Forrest, Pfizer, Theravance, and Trius.
H.J.L. consults to CSL Behring, Pharming, Dyax, Shire and ViroPharma and has acted as a speaker for CSL Behring, Viropharma and Shire.
IDZ has acted as a speaker, consultant or investigator and received honoraria from the following firms: Johnson &Johnson (Janssen-Cilag), Novartis, MSD, Pasteur, Sanofi-Aventis, GSK, Astra-Zeneca, Medtronic.
CP has acted as a speaker or consultant for Pfizer Oncology, GSK, Hoffmann-La Roche, Bayer-Schering Pharma, Novartis Pharma, Astellas, Aveo Pharmaceuticals, Boehringer-Ingelheim, and Recordati; he has also received research grants from Bayer-Schering Pharma and Novartis Pharma.
JLS has acted as a speaker for, attended advisory boards or had unrestricted educational grants from Astra-Zeneca, BMS-Otsuka, Eli-Lilly, GSK, Janssen-Cilag, Lundbeck, Sanofi-Aventis and Servier.
The bedside unit gains points for its ability to act as a decent speaker for your devices, however, and for the extra charging port it offers for your iPhone's USB cable, which means you won't have to plug in yet another device into the power bar many of us now have beside our beds.
