Conformational Stabilization of Rat S-Adenosylmethionine Decarboxylase by Putrescine

Abstract

The activity and processing of mammalian S-adenosylmethionine decarboxylase (AdoMetDC) is stimulated by putrescine. To obtain new insights into the mechanism through which putrescine stimulates AdoMetDC, we investigated conformational changes in rat prostate AdoMetDC in the presence or absence of putrescine. We examined the reactivity of purified rat prostate AdoMetDC to the SH-reagent iodoacetic acid (IAA) and its susceptibility to proteolysis in the presence or absence of putrescine using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The activity of AdoMetDC treated with IAA in the absence of putrescine was reduced, but about 80% of its activity remained after treatment with IAA in the presence of putrescine. In the presence of putrescine, IAA incorporation was 1.9 mol IAA/mol of AdoMetDC a-subunit, while there was no incorporation of IAA in the b-subunit of AdoMetDC. In the absence of putrescine, 5.0 mol of IAA/mol of a-subunit and 0.9 mol of IAA/mol of b-subunit were incorporated. Only Cys292 and Cys310 were carboxymethylated by IAA in the presence of putrescine. In contrast, in the absence of putrescine all cysteines were carboxymethylated by IAA. In addition, putrescine slowed the rate of AdoMetDC degradation by trypsin. These results demonstrate that the conformation of AdoMetDC purified from rat prostate is stabilized by putrescine.

Spermidine, a sensor for antizyme 1 expression regulates intracellular polyamine homeostasis

“…Furthermore, the inhibition of polyamine synthesis causes a compensatory increase in SAMDC activity. However, the supply of excess polyamines decreases its activity to nearly zero (Tabor and Tabor, 1984; Heby and Presson 1990b; Wada and Sirahata 2010). Wang et al showed that PUT increased SAMDC activity in IEC-6 cells (Wang et al 1992).…”

“…Spermidine/spermine–N1-Acetyltransferase (SSAT), a highly regulated enzyme plays a crucial role in maintaining polyamine homeostasis (Casero et al 2007; Pegg, 2008; Wada and Shirahata 2010). SSAT acetylates and converts SPM and SPD to SPD and PUT, respectively.…”

“…Catalyzed by the same enzymes, spermidine is converted to putrescine. The induction and activities of these enzymes are also regulated by polyamines (Casero et al 2007; Pegg 2008; Wada and Shirahata 2010). Furthermore, ODC activity itself is highly regulated and varies in response to many different stimuli in different tissues and cells.…”

Gene polymorphisms in the ornithine decarboxylase–polyamine pathway modify gastric cancer risk by interaction with isoflavone concentrations

“…Both by-products play a role in gastric carcinogenesis through DNA, RNA, protein, and membrane damage caused by reactive oxygen radicals [15]. Polyamine synthesis is stimulated by ODC and AMD [3,4]. ODC is controlled by NQO1 and ornithine decarboxylase antizyme 1 (OAZ1), and polyamines stimulate OAZ1.…”

“…Polyamine synthesis is stimulated by ODC, a rate-limiting enzyme, and S-adenosylmethionine decarboxylase (AMD), another key enzyme [3,4], and thus inhibition of ODC and AMD may be of major importance. Previous studies showed that the irreversible inhibition of ODC suppressed cancer formation [5,6].…”