Variants of PQQ-dependent glucose dehydrogenase having improved substrate specificity

A soluble pyrroloquinoline-quinone-dependent glucose dehydrogenase (sPQQGDH), comprising the amino acid sequence of SEQ ID NO:

• 22, having, compared with the sPQQGDH wild-type strain LMD 79.41 from Acinetobacter calcoaceticus, an insertion of three to five amino acids between positions Q168 and L169
• wherein said insertion is selected from the group consisting of:
• (a) an insertion of 3 amino acids, wherein the inserted amino acids have an A or G at position 1, a Y, F, or W at position 2, and a Q, L, V, or I at position 3,
• (b) an insertion of 4 amino acids, wherein the inserted amino acids have an A or G at position 1, a G, D, or L at position 2, an R or A at position 3, and an M or V at position 4, and
• (c) an insertion of 5 amino acids, wherein the inserted amino acids have an A, M, S, or V at position 1, an E, G, or S at position 2, an H, K, R, S, or T at position 3, an F, H, I, L, N, V or Y at position 4, and an F, H, L, N, Q, T, or Y at position 5.