We previously described three alpha-L-arabinofuranosidases (ABFs) secreted by Penicillium chrysogenum 31B. Here, we purified a fourth ABF, termed PcABF43A, from the culture filtrate. The molecular mass of the enzyme was estimated to be 31 kDa. PcABF43A had the highest activity at 35 degrees C and at around pH 5. The enzyme activity was strong on sugar beet L-arabinan but weak on debranched arabinan and arabinoxylan. Low molecular-mass substrates such as p-nitrophenyl alpha-L-arabinofuranoside, alpha-1,5-L-arabinooligosaccharides, and branched arabinotriose were highly resistant to the action of PcABF43A. H-1-NMR analysis revealed that PcABF43A hydrolyzed arabinosyl side chains linked to C-2 or C-3 of single-substituted arabinose residues in L-arabinan. Reports concerning enzymes specific for L-arabinan are quite limited. Pcabf43A cDNA encoding PcABF43A was isolated by in vitro cloning. The deduced amino acid sequence of the enzyme shows high similarities with the sequences of other fungal uncharacterized proteins. Semi-quantitative RT-PCR analysis indicated that the Pcabf43A gene was constitutively expressed in P. chrysogenum 31B at a low level, although the expression was induced with pectic components such as L-arabinose, L-rhamnose, and D-galacturonic acid. Analysis of enzymatic characteristics of PcABF43A, GH51 ABF (AFQ1), and GH54 ABF (AFS1) from P. chrysogenum suggested that PcABF43A and AFS1 function as debranching enzymes and AFQ1 plays a role of saccharification in the degradation of L-arabinan by this fungus. (c) 2014 Elsevier Inc. All rights reserved.