(IMAGE) National Institutes of Natural Sciences Caption This is the structural basis for steady slowness. The steric barrier prevents access of a water molecule to the catalytic site (indicated by a black dot). Credit IMS/NINS Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.