Graz University of Technology Austria Institute of Biochemistry ...

words, the hydroxyl group attacks the carbon atom in the course of the reaction. Recently, a
novel enzyme could be identified in Pseudomonas DSM 6611 (termed PISA1 = Pseudomonas
inverting alkylsulfatase 1) which mainly cleaves secondary alkylsulfates, for example 2-
octylsulfate exhibiting stereopreference for the (R)-stereoisomer. In contrast to the majority of
hydrolases, which do not alter the stereochemistry of the substrate during catalysis, PISA1 is
an attractive enzyme for the deracemisation of sec-alcohols.
Analysis of the crystal structures of PISA1 and SdsA1 showed that the overall structure of
both proteins is virtually identical and both enzymes largely share the same active-site
architecture, such as a sulfate binding site (composed of two Arg), a nucleophile site
composed of a binuclear Zn 2+ -cluster typical for metallo-ß-lactamases and an Asn/Thrhydrogen
binding network for substrate positioning. However, the active site of PISA1
features several conspicuous amino acid exchanges (see figure below: in blue active side
residues in SdsA1 and green those in PISA1).
Phe/Gly
Tyr/His
Met/Ser
Met/Ser
Leu/Pro
Ala/Ile
Tyr/Ser
Tyr/Ser
Ala/Ile
These amino acids are now subject of an extensive mutagenesis program to define their role in
governing substrate preference of the reaction. This project is a close collaboration with Profs.
Faber (biocatalysis) and Wagner (structure determination) from the University of Graz (thesis
project of Tanja Knaus in our laboratory and Markus Schober in Prof. Faber’s laboratory).
Doctoral thesis completed
Katrin Fantur: Friend or Foe: Iminosugars as inhibitors and pharmacological chaperones of
the human lysosomal acid β-galactosidase
G M1 -gangliosidosis (GM1) and Morquio B disease (MBD) are rare, hereditary lysosomal
storage disorders caused by mutations in the gene GLB1. Its main gene product, human
lysosomal acid β-galactosidase (β-Gal) degrades N-linked oligosaccharides present in
glycoproteins, GM1-gangliosides in the brain, and keratan sulfate in connective tissues. While
GM1 is a phenotypically heterogenous neurodegenerative disorder, MBD is a systemic bone
disease without effects on the central nervous system. Some mutations in the GLB1 gene
produce stable β-Gal precursors, normally transported and processed to mature,
intralysosomal β-Gal, while others affect precursor stability and intracellular transport
resulting in premature protein degradation. Several misfolded enzymes were shown to be
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