Evolutionary and biochemical differences between human and monkey acidic mammalian chitinases.

Area of Science:

• Biochemistry
• Evolutionary Biology
• Genomics

Background:

• Acidic mammalian chitinase (AMCase) is linked to asthma pathology.
• Human and mouse AMCase are well-studied, but comparative studies in closely related species are lacking.
• CHIA-like genes exist in mammals, but their functional roles vary.

Purpose of the Study:

• To compare acidic chitinase enzymes between humans and macaques.
• To identify the functional acidic chitinase gene in cynomolgus macaques.
• To characterize the novel macaque acidic chitinase enzyme.

Main Methods:

• Genome database searches for CHIA-like genes in humans and macaques.
• Tissue expression analysis of CHIA and CHIA-L1 genes in human and macaque stomach.
• Cloning and enzymatic activity assays of macaque CHIA-L1 (MACase).
• DNA sequence homology analysis.

Main Results:

• Macaque stomach tissue shows high expression of CHIA-L1 and undetectable CHIA expression, unlike humans.
• A novel macaque acidic chitinase, MACase (encoded by mCHIA-L1), was identified and cloned.
• MACase exhibits a similar pH optimum to human AMCase but is 50 times more active.
• Macaque CHIA-L1 shares higher DNA sequence identity with human CHIA-L1 pseudogene than with functional human CHIA.

Conclusions:

• Macaque CHIA-L1, not CHIA, encodes the functional acidic chitinase (MACase).
• MACase represents a distinct evolutionary trajectory for primate acidic chitinases.
• The findings highlight species-specific adaptations in acidic chitinase evolution.