In the present invention, HPPD enzymes and plants containing them showing a full tolerance against several classes of HPPD-inhibitors are described. A set of HPPD enzymes have been designed which have either no or only a significantly reduced affinity to HPPD inhibitors and, at the same time, the rate of dissociation of the HPPD inhibitors of the enzyme is increased to such an extent that the HPPD inhibitors no longer act as slow-binding or slow, tight-binding inhibitors but, instead of this, have become fully reversible inhibitors. In particular, isolated polynucleotides encoding HPPD inhibitor tolerance polypeptides are provided. Additionally, amino acid sequences corresponding to the polynucleotides are encompassed.
