Streptomyces exfoliatus SMF13 produced leupeptin, chymotrypsin-l i ke protease (CTP), metalloprotease, and trypsin-like protease (TLP) extracellularly. The activity of TLP was specifically inhibited by leupeptin. Production of leupeptin was closely associated with growth but leupeptin was inactivated by leupeptin-inactivating protein (LIP) when growth reached the stationary phase in submerged cultures, or when aerial mycelia started to form on surface cultures. Autolysis of mycelia after the stationary phase in submerged cultures was apparently retarded by the addition of leupeptin; on surface cultures, aerial mycelium formation was clearly retarded by the addition of leupeptin. We propose that CTP participates primarily in utilization of a proteinaceous nitrogen source, that TLP functions as an essential enzyme involved in the metabolism of mycelial protein, that leupeptin inhibits the activity of TLP and that LIP inactivates leupeptin. The cascade of regulatory actions of the compounds, which are produced sequentially during mycelium development, may provide selective advantages in adverse culture conditions.
Streptomyces exfoliatus SMF13 sequentially produced leupeptin, leupeptininactivating enzyme (LIE) and trypsin-like protease (TLP). TLP was produced upon exhaustion of glucose. Autolysis of mycelium was accompanied by an increase in TLP activity. However, in three bld mutants isolated from 5. exfoliatus SMF13 after UV-mutagenesis, mycelium autolysis did not occur, and neither LIE nor TLP was produced, although leupeptin was produced. Production of both LIE and TLP was restored in a spontaneous Spo+ revertant of a bld mutant. In contrast, two whi mutants sequentially produced leupeptin, LIE and TLP. The molecular mass of TLP produced during morphological differentiation was estimated to be 31.8 kDa by SDS-PAGE. The N-terminal amino acid sequence was RVGGTxAAQGNFPFQQxLSM. TLP was competitively inhibited by leupeptin; the inhibition constant was 0915 pM. TLP effectively hydrolysed the mycelial protein extract of 5. exfoliatus SMF13, but the hydrolytic activity was inhibited by leupeptin. It was concluded that morphological differentiation and production of TLP are coordinately regulated, that TLP may function as an enzyme in the metabolism of mycelial proteins, and that the hydrolytic activity of TLP is regulated by autogenous leupeptin in 5. exfoliafws SMF13.
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