The present invention refers to Amadoriase enzyme protein variants having de-glycating activity and improved thermostability compared to the wild type Amadoriase. The present invention refers also to the use of the thermostabilized Amadoriase as deglycating agent, preferably in the food industry. Moreover, the present invention refers to the use of the thermostabilized Amadoriase as diagnostic and/or therapeutic tools. Preferably, the Amadoriase enzyme protein variants of the invention can be used for determining the level of glycated haemoglobin in a biological sample and therefore for monitoring diabetes.