An ITPA Enzyme with Improved Substrate Selectivity.

Area of Science:

• Biochemistry
• Genetics
• Enzyme Engineering

Background:

• Infant deficiencies in inosine triphosphate pyrophosphatase (ITPA) can be lethal, highlighting its critical but poorly understood role in neural development.
• ITPA gene polymorphism affects patient outcomes with ribavirin and thiopurine therapies, impacting nearly one-third of the human population.
• Previous studies identified an E22A ITPA mutant with enhanced ITP hydrolysis activity via site-directed mutagenesis.

Purpose of the Study:

• To investigate the biochemical properties of ITPA mutants at position 22 through rational enzyme engineering.
• To develop an improved ITPA enzyme with enhanced substrate selectivity for therapeutic applications.

Main Methods:

• Rational enzyme engineering of the ITPA substrate selectivity pocket at position 22.
• Biochemical characterization of engineered ITPA mutants, including substrate selectivity assays.
• Assessment of biological activity of the novel E22D ITPA mutant.

Main Results:

• The E22D ITPA mutant demonstrated a two-fold improved substrate selectivity for ITP over ATP.
• The E22D ITPA mutant showed a four-fold improved substrate selectivity for ITP over GTP.
• The engineered E22D ITPA maintained its biological activity while exhibiting enhanced ITP hydrolysis.

Conclusions:

• The novel E22D ITPA mutant exhibits significantly enhanced substrate selectivity and retains biological activity.
• Engineered ITPA variants like E22D ITPA represent a promising platform for developing novel therapeutic strategies.
• Further development of E22D ITPA could lead to improved treatments for ITPA deficiencies and related conditions.