invertase, a very important enzyme in the grape berry for converting the larger molecule sucrose to its constituent molecules of glucose and fructose in the ripening fruit so that sugar develops (see sugar in grapes). The name invertase comes from the so-called ‘invert’ sugars of glucose and fructose. The reaction of this enzyme differs from that of other enzymes in that it is not reversible. This is one of the most widespread enzymes in the plant kingdom, and indeed one of the most efficient. It can metabolize 1 million times its own weight of sucrose with no loss of activity. The enzyme is located in the vacuole of berry cells, where it functions readily in the acidic environment.