Differences between homogeneous spermidine synthases isolated from rat and pig liver.

Area of Science:

• Biochemistry
• Enzymology

Background:

• Spermidine synthase is a key enzyme in polyamine biosynthesis.
• Understanding enzyme structure and function is crucial for metabolic pathway research.

Purpose of the Study:

• To purify and characterize spermidine synthase from rat and pig liver.
• To compare the biochemical and structural properties of spermidine synthase from different species.

Main Methods:

• Purification using DEAE-Sepharose, affinity chromatography, gel filtration, and electrophoresis.
• Analysis of specific activity, molecular weight, subunit composition, pI values, peptide maps, and amino acid composition.
• Enzyme inhibition assays.

Main Results:

• Spermidine synthase was purified to homogeneity from both rat and pig liver.
• Both enzymes exhibited similar specific activity, molecular weight (74,000), and subunit composition (two subunits).
• Significant differences were observed in pI values (pig: 5.16, rat: 5.34), peptide maps, and amino acid composition. The rat enzyme was more sensitive to S-adenosyl-1,8-diamino-3-thiooctane inhibition.

Conclusions:

• Rat and pig liver spermidine synthases share conserved structural and functional features.
• Species-specific variations exist in enzyme properties, including charge, peptide structure, and inhibitor sensitivity.
• These differences may reflect distinct regulatory mechanisms or evolutionary adaptations in polyamine metabolism.