BY MILDRED COHN
UNRAVELING THE glycolytic and glycogenolytic pathways was a remarkable feat and a testament to the imagination and ingenuity of all those who participated. Carl and Gerty Cori contributed an essential part and in so doing were among the pioneers who showed that biochemical investigations of isolated enzyme systems could lead to an understanding of physiological processes. From their discovery of the first product of glycogen breakdown, glucose-1-phosphate, the Coris went on to isolate and crystallize the enzyme phosphorylase that catalyzed the reaction—the first of a class of reactions in which inorganic orthophosphate reacts to yield an organic phosphate ester.
Glycogen phosphorylase proved a treasure trove for biochemistry. By reversal of the phosphorylase reaction, it was shown that a macromolecule could be synthesized in a cell-free system. The enzyme was further found to exist in two interconvertible forms, though one was inactive in the absence of adenylic acid, which acted as an effector. The next generation of scientists trained in the Cori laboratory, using the Coris' fundamental discoveries, probed still further and discovered the two most widespread metabolic regulatory mechanisms: the cyclic AMP system and phos-