Required for the maturation of SdpC to SDP (PubMed:12817086). Not required for SdpC signal peptide cleavage, secretion from the cell or disulfide bond formation (PubMed:23687264). By Spo0A during nutrient starvation (PubMed:12817086). Repressed by AbrB during regular growth when nutrients are plentiful, in association with the transcriptional repressor Abh. When the sdpA-sdpB-sdpC operon is deleted, increased rate of spore formation; a double operon deletion (sdpA-sdpC plus skfA-skfH) makes spores even faster (PubMed:12817086). A single deletion mutant does not have SDP activity (active peptide of sdpC) (PubMed:23687264).