synthase

[sĭnthās′, -thāz′]
n.
  1. Any of various enzymes that catalyze the synthesis of a substance without the use of a high-energy source such as cleavage of a phosphate bond in ATP.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.