The relationship between the violet pigment PP-V production and intracellular ammonium level in Penicillium purpurogenum.

Ryo Kojima,Hiroshi Matsufuji,Taisuke Watanabe,Teppei Arai,Jun Ogihara,Takafumi Kasumi

doi:10.1186/s13568-016-0215-y

Abstract

Penicillium purpurogenum is the fungus that produces an azaphilone pigment. However, details about the pigment biosynthesis pathway are unknown. The violet pigment PP-V is the one of the main pigments biosynthesized by this fungus. This pigment contains an amino group in a pyran ring as its core structure. We focused on this pigment and examined the relationship between intracellular ammonium concentration and pigment production using glutamine as a nitrogen source. The intracellular ammonium level decreased about 1.5-fold in conditions favoring PP-V production. Moreover, P. purpurogenum was transferred to medium in which it commonly produces the related pigment PP-O after cultivating it in the presence or absence of glutamine to investigate whether this fungus biosynthesizes PP-V using surplus ammonium in cells. Only mycelia cultured in medium containing 10 mM glutamine produced the violet pigment, and simultaneously intracellular ammonium levels decreased under this condition. From comparisons of the amount of PP-V that was secreted with quantity of surplus intracellular ammonium, it is suggested that P. purpurogenum maintains ammonium homeostasis by excreting waste ammonium as PP-V.

Highlights

The filamentous fungus Penicillium purpurogenum IAM15392, isolated from soil, produces PP-Y, PP-O, PP-V, and PP-R as Monascus pigments under specific medium conditions (Ogihara and Oishi 2002; Ogihara et al 2000a, b, 2001)
P. purpurogenum was transferred to medium in which it commonly produces the related pigment PP-O after cultivating it in the presence or absence of glutamine to investigate whether this fungus biosynthesizes PP-V using surplus ammonium in cells
To verify that PP-V that detected as extracellular pigment on glutamine medium is biosynthesized in the cell, we investigated whether it was obtained from reactants of PP-O and glutamine by in vitro, and analyzed intracellular pigment by thin layer chromatography (TLC)

Summary

Introduction

The filamentous fungus Penicillium purpurogenum IAM15392, isolated from soil, produces PP-Y, PP-O, PP-V, and PP-R as Monascus pigments under specific medium conditions (Ogihara and Oishi 2002; Ogihara et al 2000a, b, 2001). Monascus pigments have been used as a natural food colorant in East Asia. Attention has been focused on these compounds due to their antimicrobial (Kim et al 2006), anticancer (Zheng et al 2010), and antioxidizing (Akihisa et al 2005) activities. A nephrotoxic mycotoxin called citrinin is produced by some Monascus spp. For this reason, in Europe and the United States, use of Monascus pigments is banned (Mapari et al 2010).

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